EXECUTION COPY

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                          AGREEMENT AND PLAN OF MERGER

                             DATED AS OF MAY 6, 2001

                                 BY AND BETWEEN

                            VALERO ENERGY CORPORATION

                                       AND

                      ULTRAMAR DIAMOND SHAMROCK CORPORATION

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                                TABLE OF CONTENTS


ARTICLE I      CERTAIN DEFINITIONS............................................ 4

ARTICLE II        THE MERGER................................................. 12
   2.1   The Merger.......................................................... 12
   2.2   Effective Time of the Merger........................................ 12
   2.3   Effects of the Merger............................................... 12
   2.4   Closing............................................................. 12
   2.5   Certificate of Incorporation........................................ 12
   2.6   By-Laws............................................................. 12
   2.7   Directors and Officers.............................................. 12

ARTICLE III       CONVERSION OF SECURITIES................................... 13
   3.1   Effect of the Merger on Capital Stock............................... 13
   3.2   Stock Options....................................................... 16
   3.3   Exchange Fund....................................................... 17
   3.4   Exchange Procedures................................................. 17
   3.5   Distributions with Respect to Unexchanged Shares.................... 18
   3.6   No Further Ownership Rights in UDS Common Stock..................... 18
   3.7   No Fractional Shares of Valero Common Stock......................... 18
   3.8   Termination of Exchange Fund........................................ 19
   3.9   No Liability........................................................ 19
   3.10  Investment of the Exchange Fund..................................... 19
   3.11  Lost Certificates................................................... 19
   3.12  Withholding Rights.................................................. 19
   3.13  Further Assurances.................................................. 19
   3.14  Stock Transfer Books................................................ 20

ARTICLE IV        REPRESENTATIONS AND WARRANTIES............................. 20
   4.1   Representations and Warranties of UDS............................... 20
   4.2   Representations and Warranties of Valero............................ 30

ARTICLE V         COVENANTS RELATING TO CONDUCT OF BUSINESS.................. 38
   5.1   Covenants of UDS.................................................... 38
   5.2   Covenants of Valero................................................. 41
   5.3   Governmental Filings................................................ 42
   5.4   Control of Other Party's Business................................... 42

ARTICLE VI        ADDITIONAL AGREEMENTS...................................... 42
   6.1   Preparation of Proxy Statement; Stockholders Meetings............... 42
   6.2   Valero Board of Directors........................................... 44
   6.3   Access to Information............................................... 44
   6.4   Reasonable Best Efforts............................................. 44
   6.5   Acquisition Proposals............................................... 46
   6.6   Fees and Expenses................................................... 47
   6.7   Directors' and Officers' Indemnification and Insurance.............. 47
   6.8   Employee Benefits................................................... 48
   6.9   Public Announcements................................................ 49
   6.10  Listing of Shares of Valero Common Stock............................ 50
   6.11  Rights Agreements................................................... 50
   6.12  Affiliates.......................................................... 50
   6.13  Section 16 Matters.................................................. 50
   6.14  UDS Indebtedness.................................................... 50
   6.15  Accountants' Letter................................................. 51

ARTICLE VII       CONDITIONS PRECEDENT....................................... 51
   7.1   Conditions to Each Party's Obligation to Effect the Merger.......... 51
   7.2   Additional Conditions to Obligations of Valero...................... 51
   7.3   Additional Conditions to Obligations of UDS......................... 52

ARTICLE VIII      TERMINATION AND AMENDMENT.................................. 53
   8.1   Termination......................................................... 53
   8.2   Effect of Termination............................................... 54
   8.3   Amendment........................................................... 56
   8.4   Extension; Waiver................................................... 56

ARTICLE IX        GENERAL PROVISIONS......................................... 56
   9.1   Non-Survival of Representations, Warranties and Agreements.......... 56
   9.2   Notices............................................................. 56
   9.3   Interpretation...................................................... 57
   9.4   Counterparts........................................................ 58
   9.5   Entire Agreement; No Third Party Beneficiaries...................... 58
   9.6   Governing Law....................................................... 58
   9.7   Severability........................................................ 58
   9.8   Assignment.......................................................... 58
   9.9   Submission to Jurisdiction; Waivers................................. 58
   9.10  Enforcement......................................................... 59

EXHIBIT A - Form of Affiliate Letter


                  AGREEMENT  AND PLAN OF  MERGER,  dated as of May 6, 2001 (this
"Agreement"),  by and between VALERO ENERGY CORPORATION,  a Delaware corporation
("Valero") and ULTRAMAR DIAMOND  SHAMROCK  CORPORATION,  a Delaware  corporation
("UDS").

                              W I T N E S S E T H:

                  WHEREAS,  the  Boards  of  Directors  of  Valero  and UDS have
approved the  transactions  contemplated by this Agreement and have  recommended
the adoption of this Agreement by their respective shareholders; and

                  WHEREAS, for Federal income tax purposes,  it is intended that
the Merger  shall  qualify as a  "reorganization"  within the meaning of Section
368(a) of the Internal  Revenue Code of 1986, as amended (the  "Code"),  and the
regulations promulgated thereunder.

                  NOW,  THEREFORE,  in  consideration  of the  foregoing and the
respective  representations,  warranties,  covenants and agreements set forth in
this  Agreement,  and intending to be legally bound hereby,  the parties  hereto
agree as follows:

                                   ARTICLE I
                               CERTAIN DEFINITIONS

                  As used in this Agreement,  the following terms shall have the
respective meanings set forth below:

                  "Acquisition  Proposal"  shall have the  meaning  set forth in
Section 6.5(a)(i).

                  "Affiliate"  shall  have the  meaning  given such term in Rule
12b-2 under the Exchange Act.

                  "Affiliate  Agreement"  shall  have the  meaning  set forth in
Section 6.12.

                  "Agreement" shall have the meaning set forth in the preamble.

                  "Assumed  Indentures"  shall  have the  meaning  set  forth in
Section 6.14.

                  "beneficial  ownership" or  "beneficially  own" shall have the
meaning  ascribed to such terms under  Section 13(d) of the Exchange Act and the
rules and regulations thereunder.

                  "Benefit Plan" means, with respect to any entity, any employee
compensation,  benefit plan, program, policy, practice,  agreement,  contract or
other arrangement providing benefits to any current or former employee,  officer
or director  of such entity or any of its  Subsidiaries  or any  beneficiary  or
dependent  thereof that is sponsored or  maintained by such entity or any of its
Subsidiaries or to which such entity or any of its  Subsidiaries  contributes or
is  obligated  to  contribute,   whether  or  not  written,   including  without
limitation, any employee welfare benefit plan within the meaning of Section 3(1)
of ERISA,  any employee  pension benefit plan within the meaning of Section 3(2)
of  ERISA  (whether  or not  such  plan is  subject  to  ERISA)  and any  bonus,
incentive,  deferred  compensation,  vacation,  stock  purchase,  stock  option,
severance, employment, change of control or fringe benefit plan, program, policy
or agreement and any related trusts or other funding vehicles.

                  "Benefit  Protection  Period" shall have the meaning set forth
in Section 6.8(a).

                   "Business  Day" means any day on which banks are not required
or authorized to close in the City of New York.

                  "Cash  Consideration"  shall  have the  meaning  set  forth in
Section 3.1(b).

                  "Cash Consideration  Formula" shall have the meaning set forth
in Section 3.1(b).

                  "Cash  Election"  shall have the  meaning set forth in Section
3.1(f)(i).

                  "Cash  Election  Shares"  shall have the  meaning set forth in
Section 3.l(g).

                  "Cash Election Number" shall mean,  subject to Section 3.1(k),
the quotient,  rounded to the nearest whole share,  obtained by dividing (x) the
product of 27.5 and the UDS Closing Share Number by (y) the Cash  Consideration;
provided,  however,  that, if the Cash Election Number as so determined  exceeds
50% of the UDS Closing Share Number,  Valero may in its discretion set a maximum
Cash Election  Number at any lesser number so long as such maximum Cash Election
Number equals or exceeds 50% of the UDS Closing Share Number.

                  "Cash  Fraction"  shall have the  meaning set forth in Section
3.1(g).

                  "CERCLA"  means  the  Comprehensive   Environmental  Response,
Compensation and Liability Act of 1980, as amended.

                  "Certificate  of Merger"  shall have the  meaning set forth in
Section 2.2.

                  "Change in the UDS Recommendation"  shall have the meaning set
forth in Section 6.1(b).

                  "Change in the Valero  Recommendation"  shall have the meaning
set forth in Section 6.1(c).

                  "Closing" shall have the meaning set forth in Section 2.4.

                  "Closing  Date"  shall have the  meaning  set forth in Section
2.4.

                  "Code" shall have the meaning set forth in the recitals.

                  "Confidentiality  Agreement"  shall have the meaning set forth
in Section 6.3.

                  "DGCL" means the Delaware General Corporation Law.

                  "Dissenting  Shares"  shall  have  the  meaning  set  forth in
Section 3.1(e).

                  "DOJ" means the Antitrust Division of  the  U.S. Department of
Justice.

                  "Effective  Time"  shall have the meaning set forth in Section
2.2.

                  "Election  Deadline"  shall  have  the  meaning  set  forth in
Section 3.1(j).

                  "Employee  Grantor Trust" shall mean the UDS Employee Benefits
Trust created by the Trust Agreement,  effective as of November 9, 1999, between
UDS and Sterling National Bank, a national banking association, as Trustee.

                   "ERISA" means the Employee  Retirement Income Security Act of
1974, as amended.

                  "ERISA Affiliate" means, with respect to any entity,  trade or
business,  any  other  entity,  trade or  business  that is a member  of a group
described in Section 414(b),  (c), (m) or (o) of the Code or Section  4001(b)(1)
of ERISA that includes the first entity, trade or business,  or that is a member
of the same "controlled  group" as the first entity,  trade or business pursuant
to Section 4001(a)(14) of ERISA.

                  "ESOP" has the meaning set forth in Section 4.1(l)(xi).

                  "Exchange Act" means the  Securities  Exchange Act of 1934, as
amended.

                  "Exchange  Agent"  shall have the meaning set forth in Section
3.3.

                  "Exchange  Fund"  shall have the  meaning set forth in Section
3.3.

                  "Exchange  Ratio"  shall  mean the  quotient,  rounded  to the
nearest  ten-thousandth,  obtained by dividing (i) the sum of (a) $27.50 and (b)
the product of (I) 0.614 and (II) the Valero Average  Closing Price) by (ii) the
Valero Average Closing Price.

                  "Expenses"  means all  out-of-pocket  expenses  (including all
fees and  expenses  of counsel,  accountants,  investment  bankers,  experts and
consultants to a party and its affiliates)  incurred by a party or on its behalf
in connection with or related to the  authorization,  preparation,  negotiation,
execution and  performance of this Agreement and the  transactions  contemplated
hereby,  including the  preparation,  printing,  filing and mailing of the Joint
Proxy  Statement/Prospectus and the Form S-4 and the solicitation of stockholder
approvals and all other matters related to the transactions  contemplated hereby
and thereby.

                  "Form  S-4"  shall  have the  meaning  set  forth  in  Section
4.1(d)(iii).

                  "Form of Election" shall have the meaning set forth in Section
3.1(f).

                  "FTC" means the U.S. Federal Trade Commission.

                  "GAAP" means U.S. generally accepted accounting principles.

                  "Governmental  Entity"  shall  have the  meaning  set forth in
Section 4.1(d)(vii).

                  "GSOP" shall have the meaning set forth in Section 3.1(d).

                  "HSR Act" means the Hart-Scott-Rodino  Antitrust  Improvements
Act of 1976, as amended.

                  "Intellectual Property" means all patents,  trademarks,  trade
names, service marks,  copyrights,  and any applications  therefor,  technology,
know-how, computer software programs or applications, and tangible or intangible
proprietary information or materials.

                  "Joint Proxy  Statement/Prospectus" shall have the meaning set
forth in Section 4.1(d)(iii).

                  "knowledge" or "known" means, with respect to any entity,  the
knowledge of such entity's executive officers after reasonable inquiry.

                  "Letter of  Transmittal"  shall have the  meaning set forth in
Section 3.4(a).

                  "Liens"   shall  have  the   meaning   set  forth  in  Section
4.1(b)(ii).

                  "Loan" shall have the meaning set forth in Section 4.1(l)(xi).

                  "Material Adverse Effect" means, with respect to any entity, a
material adverse effect on (i) the business,  operations,  results of operations
or financial  condition of such entity and its Subsidiaries  taken as a whole or
(ii)  the  ability  of  such  entity  to  timely   consummate  the  transactions
contemplated by this Agreement,  except, in each case, to the extent such effect
is  reasonably  attributable  to (x) general  economic  conditions in the United
States  (including  prevailing  interest rate and stock market levels),  (y) the
general  state  of the  industries  in which  such  entity  operates  or (z) the
negotiation,   announcement,   execution,   delivery  or   consummation  of  the
transactions contemplated by, or in compliance with, this Agreement.

                  "Merger" shall have the meaning set forth in Section 2.1.

                  "Merger  Consideration"  shall have the  meaning  set forth in
Section 3.1(b).

                  "Multiemployer Plan" means any "multiemployer plan" within the
meaning of Section 4001(a)(3) of ERISA.

                  "Multiple  Employer  Plan" shall have the meaning set forth in
Section 4.1(l)(vi).

                  "Necessary  Consents"  shall  have the  meaning  set  forth in
Section 4.1(d)(vi).

                  "New  Plans"  shall  have the  meaning  set  forth in  Section
6.8(b).

                  "Non-Election"  shall  have the  meaning  set forth in Section
3.1(f).

                  "Non-Election  Cash Fraction" shall have the meaning set forth
in Section 3.1(i).

                  "Non-Election  Shares"  shall  have the  meaning  set forth in
Section 3.l(g).

                  "Non-Subsidiary Affiliate" shall have the meaning set forth in
Section 4.1(b)(ii).

                  "NYSE" means the New York Stock Exchange, Inc.

                  "Old  Plans"  shall  have the  meaning  set  forth in  Section
6.8(b).

                  "Other  Approvals" shall have the meaning set forth in Section
4.1(d)(ii).

                  "other  party"  means,  with respect to Valero,  UDS, and with
respect to UDS, Valero.

                  "Partial  Cash  Election"  shall have the meaning set forth in
Section 3.1(f)(ii).

                  "Person" means an individual,  corporation,  limited liability
company,  partnership,  association,  trust, unincorporated organization,  other
entity or group (as defined in the Exchange Act).

                  "PBGC" shall have the meaning set forth in Section 4.1(l)(v).

                  "Regulatory  Law"  means the HSR Act,  and all other  federal,
state and  foreign,  if any,  statutes,  rules,  regulations,  orders,  decrees,
administrative  and  judicial  doctrines  and other  laws that are  designed  or
intended to prohibit,  restrict or regulate (i) mergers,  acquisitions  or other
business  combinations,  (ii) foreign  investment,  or (iii) actions  having the
purpose  or effect of  monopolization  or  restraint  of trade or  lessening  of
competition.

                  "Required  Approvals"  shall  have the  meaning  set  forth in
Section 6.4(a)(i).

                  "SEC" means the U.S. Securities and Exchange Commission.

                  "Securities Act" means the Securities Act of 1933, as amended.

                  "Significant  Subsidiary"  shall have the meaning  ascribed to
such term in Rule 1-02 of Regulation S-X of the SEC.

                  "Stock  Consideration"  shall  have the  meaning  set forth in
Section 3.1(b)(i).

                  "Stock  Election"  shall have the meaning set forth in Section
3.1(f)(iii).

                  "Stock  Election  Number"  shall  mean the UDS  Closing  Share
Number minus the Cash Election Number.

                  "Stock  Election  Shares"  shall have the meaning set forth in
Section 3.l(g).

                  "Stock  Fraction"  shall have the meaning set forth in Section
3.1(h).

                  "Subsidiary"  shall have the meaning  ascribed to such term in
Rule 1-02 of Regulation S-X of the SEC.

                  "Superior  Proposal"  means,  with respect to UDS, a bona fide
written  proposal made by a Person other than a party to this Agreement which is
(i) an Acquisition Proposal involving UDS and (ii) is on terms which UDS's Board
of Directors  in good faith  concludes  (following  receipt of the advice of its
financial  advisors  and  outside  counsel),  taking into  account,  among other
things, all legal,  financial,  regulatory and other aspects of the proposal and
the  Person  making  the  proposal,  (x)  would,  if  consummated,  result  in a
transaction  that is more favorable to its  stockholders (in their capacities as
stockholders),   from  a  financial  point  of  view,   than  the   transactions
contemplated by this Agreement and (y) is reasonably capable of being completed.

                  "Surviving  Corporation"  shall have the  meaning set forth in
Section 2.1.

                  "Taxes" means any and all federal,  state,  local,  foreign or
other  taxes  or  charges  of any  kind  (together  with  any and all  interest,
penalties, additions to tax and additional amounts imposed with respect thereto)
imposed by any taxing  authority,  including  taxes or other  charges on or with
respect  to income,  franchises,  windfall  or other  profits,  gross  receipts,
property,  sales,  use,  capital stock,  payroll,  employment,  social security,
workers'  compensation,  unemployment  compensation,  or net worth, and taxes or
other charges in the nature of excise, withholding, ad valorem or value added.

                  "Tax  Return"  means any return,  report or similar  statement
(including any attached schedules) required to be filed with respect to any Tax,
including  any  information  return,   claim  for  refund,   amended  return  or
declaration of estimated Tax.

                  "Termination Date" shall have the meaning set forth in Section
8.1(b).

                  "UDS" shall have the meaning set forth in the preamble.

                  "UDS 2000 10-K" means UDS's Annual Report on Form 10-K for the
fiscal year ended December 31, 2000, as filed with the SEC.

                  "UDS  Benefit  Plan"  means  each UDS Stock Plan and any other
Benefit Plan  maintained or  contributed to by UDS or a Subsidiary of UDS, or to
which UDS or any Subsidiary of UDS is required to contribute.

                  "UDS  Plan"   means  any  UDS   Benefit   Plan  other  than  a
Multiemployer Plan.

                  "UDS  Board  Designees"  shall have the  meaning  set forth in
Section 6.2.

                  "UDS  Capital  Stock"  shall  have the  meaning  set  forth in
Section 4.1(b)(i)(B).

                  "UDS Certificate"  shall have the meaning set forth in Section
3.1(b).

                  "UDS Closing  Share Number" shall mean the number of shares of
UDS Common Stock issued and outstanding immediately prior to the Effective Time,
other  than such  shares  that are to be  cancelled  in the Merger  pursuant  to
Section 3.1(a) hereof.

                  "UDS Common  Stock"  means common  stock,  par value $0.01 per
share, of UDS.

                  "UDS  Contract"  shall have the  meaning  set forth in Section
4.1(j)(i).

                  "UDS  Converted  Option"  shall have the  meaning set forth in
Section 3.2(a).

                  "UDS Disclosure  Schedule" shall have the meaning set forth in
Section 4.1.

                  "UDS  Employees"  shall have the  meaning set forth in Section
6.8(a).

                  "UDS Indebtedness" shall have the meaning set forth in Section
5.1(g)(ii).

                  "UDS  Preferred  Stock"  shall have the  meaning  set forth in
Section 4.1(b)(i)(B).

                  "UDS  Qualified  Plans"  shall have the  meaning  set forth in
Section 4.1(l)(iii).

                  "UDS  Recommendation"  shall  have the  meaning  set  forth in
Section 6.1(b).

                  "UDS  Restricted  Stock"  shall mean all shares of  restricted
stock  outstanding  under the terms of any UDS Benefit Plan immediately prior to
the Effective  Time that continue to be subject to  restrictions  on transfer or
otherwise remain unvested  pursuant to the terms thereof  immediately  following
the merger.

                  "UDS Right"  means any of the Rights,  as such term is defined
in the UDS Rights Agreement.

                  "UDS Rights Agreement" means the Rights Agreement, dated as of
June 25, 1992, as amended on October 26, 1992,  May 10, 1994,  and September 22,
1996, between UDS and First City, Texas-Houston, National Association, as rights
agent.

                  "UDS SEC  Documents"  shall  have  the  meaning  set  forth in
Section 4.1(e).

                  "UDS Stock Option" shall have the meaning set forth in Section
3.2(a).

                  "UDS Stock  Plans" shall have the meaning set forth in Section
4.1(b)(i).

                  "UDS Stockholder Approval" shall have the meaning set forth in
Section 4.1(c)(i).

                  "UDS Stockholders Meeting" shall have the meaning set forth in
Section 4.1(c)(i).

                  "UDS  Toprs"  means  the  8.32%  Trust  Originated   Preferred
Securities of UDS Capital I, a wholly owned subsidiary of UDS.

                  "UDS Termination Fee" means $125,000,000.

                  "Valero" shall have the meaning set forth in the preamble.

                  "Valero 2000  10-K"  means Valero's Annual Report on Form 10-K
for the fiscal year ended December 31, 2000, as filed with the SEC.

                  "Valero  Average Closing Price" means the average of the daily
last sale prices of Valero  Common Stock as reported on the NYSE (as reported in
the Wall Street Journal or, if not reported therein,  in another mutually agreed
upon  authoritative  source) for the ten consecutive  full trading days in which
such  shares are traded on the NYSE  ending at the close of trading on the third
business day prior to the Closing Date.

                  "Valero  Benefit  Plan" means each  Valero  Stock Plan and any
other  Benefit Plan  maintained or  contributed  to by Valero or a Subsidiary of
Valero,  or to  which  Valero  or  any  Subsidiary  of  Valero  is  required  to
contribute.

                  "Valero  Plan"  means any  Valero  Benefit  Plan  other than a
Multiemployer Plan.

                  "Valero  Capital  Stock"  shall have the  meaning set forth in
Section 4.2(b)(i)(B).

                  "Valero Common Stock" means common stock,  par value $0.01 per
share, of Valero.

                  "Valero  Contract" shall have the meaning set forth in Section
4.2(j).

                  "Valero Disclosure  Schedule" shall have the meaning set forth
in Section 4.2.

                   "Valero  Preferred Stock" shall have the meaning set forth in
Section 4.2(b)(i)(B).

                  "Valero  Qualified  Plans" shall have the meaning set forth in
Section 4.2(l)(i).

                  "Valero  Recommendation"  shall have the  meaning set forth in
Section 6.1(c).

                  "Valero  Rights"  shall have the  meaning set forth in Section
3.1(b).

                  "Valero Rights  Agreement" shall have the meaning set forth in
Section 3.1(b).

                  "Valero  SEC  Documents"  shall have the  meaning set forth in
Section 4.2(e).

                  "Valero  Stock  Option"  shall have the  meaning  set forth in
Section 3.2(a).

                  "Valero  Stock  Plans"  shall  have the  meaning  set forth in
Section 4.2(b)(i).

                  "Valero Stockholder Approval" shall have the meaning set forth
in Section 4.2(c)(i).

                  "Valero Stockholders Meeting" shall have the meaning set forth
in Section 4.2(c)(i).

                  "Valero Termination Fee" means $125,000,000.

                  "Voting  Debt"  means any  bonds,  debentures,  notes or other
indebtedness having the right to vote on any matters on which holders of capital
stock of the same issuer may vote.

                  "Withdrawal Liability" means liability to a Multiemployer Plan
as a result of a complete or partial withdrawal from such Multiemployer Plan, as
those terms are defined in Part I of Subtitle E of Title IV of ERISA.

                                   ARTICLE II
                                   THE MERGER

2.1 The Merger.  Upon the terms and  subject to the  conditions  hereof,  at the
Effective  Time, UDS shall be merged (the  "Merger") with and into Valero,  with
Valero as the surviving corporation in the Merger (the "Surviving Corporation"),
and the separate existence of UDS shall thereupon cease.

2.2 Effective Time of the Merger. The Merger shall become effective as set forth
in a properly  executed  certificate  of merger duly filed with the Secretary of
State of the State of Delaware (the "Certificate of Merger"), which filing shall
be made on the Closing  Date.  As used in this  Agreement,  the term  "Effective
Time"  shall mean the date and time when the Merger  becomes  effective,  as set
forth in the Certificate of Merger.

2.3  Effects of the Merger.  The Merger  shall have the effects set forth in the
applicable  provisions  of the DGCL.  Without  limiting  the  generality  of the
foregoing,  and subject  thereto,  at the  Effective  Time,  except as otherwise
provided herein, all of the property, rights, privileges,  powers and franchises
of UDS shall vest in the Surviving Corporation,  and all debts,  liabilities and
duties of UDS shall become the debts,  liabilities  and duties of the  Surviving
Corporation.

2.4 Closing.  Upon the terms and subject to the  conditions set forth in Article
VII and the  termination  rights set forth in Article  VIII,  the closing of the
transactions  contemplated  by this Agreement (the "Closing") will take place at
the offices of Wachtell,  Lipton,  Rosen & Katz, 51 West 52nd Street,  New York,
New  York,  10019 at  10:00  A.M.  on the  second  Business  Day  following  the
satisfaction or waiver (subject to applicable law) of the conditions  (excluding
conditions  that, by their nature,  cannot be satisfied  until the Closing Date)
set forth in Article VII, unless this Agreement has been theretofore  terminated
pursuant  to its terms or  unless  another  place,  time or date is agreed to in
writing by the parties  hereto (the date of the Closing being referred to herein
as the "Closing Date").

2.5  Certificate of  Incorporation.  At the Effective  Time, the  Certificate of
Incorporation  of  the  Surviving   Corporation  shall  be  the  Certificate  of
Incorporation of Valero,  as in effect  immediately prior to the Effective Time,
until thereafter changed or amended as provided therein or by applicable law.

2.6  By-Laws. The  by-laws  of  Valero  as  in  effect  immediately prior to the
Effective Time shall be the by-laws of the Surviving Corporation.

2.7  Directors and  Officers.  The directors and officers of Valero  immediately
prior to the Effective Time shall be the directors and officers of the Surviving
Corporation, except as provided in Section 6.2.

                                  ARTICLE III
                            CONVERSION OF SECURITIES

3.1 Effect of the Merger on Capital Stock.  At the Effective  Time, by virtue of
the Merger and without any action on the part of any holder of any capital stock
of UDS:

        (a) All shares of capital stock of UDS that are held by UDS as  treasury
stock or  that  are  owned  by Valero or any wholly-owned subsidiaries of UDS or
Valero immediately prior to the Effective Time shall cease to be outstanding and
shall be cancelled and retired and shall cease to exist.

        (b) Subject  to  Sections  3.1(a),  3.1(c), 3.1(d), 3.1(e) and 3.7, each
outstanding share of UDS Common Stock  (together with any associated UDS Rights)
issued  and  outstanding  immediately  prior  to  the  Effective  Time  shall be
converted into the right to receive, at the option of the holder as contemplated
by  Sections 3.1(f)  through  3.1(j),  either  (i)  a number of shares of Valero
Common Stock equal to the Exchange Ratio (the "Stock Consideration")  or (ii) an
amount in cash equal to the sum of (said formula being referred to herein as the
"Cash Consideration Formula") (x) $27.50 and (y) the  product  of (I) 0.614  and
(II) the Valero Average  Closing  Price (the "Cash  Consideration"  and together
with the  Stock Consideration  and the shares of Valero Common Stock issued pur-
suant  to Section 3.1(d), the "Merger Consideration").  All  of  the  shares  of
Valero  Common  Stock  to  be  issued  as  Merger  Consideration   shall be duly
authorized, validly issued, fully  paid,  nonassessable  and free of  preemptive
rights,  with  no  personal  liability  attaching to the ownership thereof.  One
preferred share purchase right issuable pursuant to the Rights Agreement,  dated
as of July 17, 1997, between Valero and Computershare Investor Services, LLC, as
successor  rights agent to Harris  Trust and Savings  Bank (the  "Valero  Rights
Agreement"),  or any other  purchase right issued in  substitution  thereof (the
"Valero  Rights"),  shall be issued together with and shall attach to each share
of Valero  Common  Stock  issued  pursuant  to this  Section  3.1(b) and Section
3.1(d),  subject and pursuant to the terms of the Valero Rights  Agreement.  All
shares of UDS  Common  Stock  converted  into the right to  receive  the  Merger
Consideration  pursuant to this Section 3.1(b) and Section 3.1(d) shall cease to
be outstanding  and shall be canceled and retired and shall cease to exist,  and
each  holder of a  certificate  that  immediately  prior to the  Effective  Time
represented  any such  shares of UDS Common  Stock (a "UDS  Certificate")  shall
thereafter  cease to have any rights  with  respect to such shares of UDS Common
Stock,  except the right to receive  the  Merger  Consideration  to be issued in
consideration therefor and any dividends or other distributions to which holders
of UDS Common Stock become entitled all in accordance with this Article III upon
the surrender of such UDS Certificate.

        (c) If, between the date of this Agreement and the Effective Time, there
is a reclassification,  recapitalization, stock split, split-up, stock dividend,
combination  or exchange of shares with respect to, or rights  issued in respect
of, UDS Common Stock or Valero Common Stock,  each of the Exchange Ratio and the
Cash Consideration Formula shall be adjusted  accordingly,  without duplication,
to  provide  to the  holders of UDS  Common  Stock the same  economic  effect as
contemplated by this Agreement prior to such event.

        (d)  Subject to Section  3.7,  each share held as of the  Effective Time
in the Employee  Grantor Trust pursuant to the UDS Grantor Trust Stock Ownership
Program  ("GSOP"),  each  share of UDS  Restricted  Stock and each  share of UDS
Common Stock that is owned by any UDS Benefit  Plan shall be converted  into the
right to  receive  a number  of fully  paid and  nonassessable  shares of Valero
Common Stock equal to the Exchange Ratio.

        (e) Notwithstanding any other provision contained in this Agreement,  no
shares of UDS Common Stock that are issued and  outstanding  as of the Effective
Time  and  that  are  held by a  stockholder  who has  properly  exercised  such
stockholder's  appraisal  rights  (any such shares  being  referred to herein as
"Dissenting Shares") under the DGCL shall be converted into the right to receive
the Merger  Consideration  as provided in Section  3.1(b)  unless and until such
stockholder shall have failed to perfect, or shall have effectively withdrawn or
lost, such stockholder's  right to dissent from the Merger under the DGCL and to
receive such  consideration  as may be determined to be due with respect to such
Dissenting  Shares  pursuant to and subject to the  requirements of the DGCL. If
any such  stockholder  shall have  failed to  perfect or shall have  effectively
withdrawn  or lost  such  right  prior to the  Election  Deadline,  each of such
holder's shares of UDS Common Stock shall thereupon be deemed to be Non-Election
Shares for all purposes of this Article III. If any holder of Dissenting  Shares
shall  have so failed  to  perfect  or has  effectively  withdrawn  or lost such
stockholder's right to dissent from the Merger after the Election Deadline, each
of such  holder's  shares of UDS Common Stock shall  thereupon be deemed to have
been converted into and to have become,  as of the Effective  Time, the right to
receive the Stock  Consideration  or the Cash  Consideration,  or a  combination
thereof, as determined by Valero in its sole discretion.

        (f) Subject to the provisions of this Section 3.1, each record holder of
shares of UDS Common Stock  outstanding  immediately prior to the Effective Time
to be  converted  in the Merger  pursuant to Section  3.1(b) will be entitled to
elect to receive  either  (i) the Cash  Consideration  for all of such  holder's
shares ("Cash  Election"),  (ii) the Cash  Consideration  for a stated number of
such holder's  shares and a number of shares of Valero Common Stock equal to the
Exchange  Ratio per share of UDS Common  Stock for the balance of such  holder's
shares of UDS Common Stock ("Partial Cash Election") or (iii) a number of shares
of Valero Common Stock equal to the Exchange Ratio per share of UDS Common Stock
for all of such holder's shares of UDS Common Stock ("Stock Election"). All Cash
Elections, Partial Cash Elections and Stock Elections shall be unconditional and
made on a form  designed for that  purpose and mutually  agreeable to Valero and
UDS (a "Form of Election"). Any holder of UDS Common Stock who fails to properly
make a Cash Election, Partial Cash Election or Stock Election and any holder who
fails to submit to the  Exchange  Agent a  properly  completed  and  signed  and
properly and timely submitted Form of Election shall be deemed to have indicated
no  preference  as to the receipt of cash or Valero Common Stock with respect to
such  holder's  shares (a  "Non-Election")  and will receive for such UDS Common
Stock the Merger Consideration described in Section 3.1(g), 3.1(h) or 3.1(i), as
applicable.  Notwithstanding any other provision set forth herein, the aggregate
number of shares of UDS Common Stock to be  converted  into the right to receive
cash in the Merger (which shall for this purpose be deemed to include Dissenting
Shares, if any) shall be equal to the Cash Election Number.

        (g) If the  aggregate  number of shares of UDS  Common  Stock  for which
cash is elected under a Cash Election or a Partial Cash Election and  Dissenting
Shares,  if any  (collectively,  the "Cash Election  Shares"),  exceeds the Cash
Election  Number,  then all shares of UDS Common Stock for which  Valero  Common
Stock was elected under a Stock Election or Partial Cash Election (collectively,
the "Stock  Election  Shares")  and all shares of UDS  Common  Stock  covered by
Non-Elections (the  "Non-Election  Shares") shall be converted into the right to
receive Valero Common Stock, and the Cash Election Shares (other than Dissenting
Shares)  shall be  converted  into the right to receive  cash and Valero  Common
Stock in the following manner:

                           Each  Cash  Election  Share  (other  than  Dissenting
                  Shares)  shall be  converted  into the right to receive (A) an
                  amount  of  cash  (rounded  to  the  nearest  cent),   without
                  interest,  equal to the product of (x) the Cash  Consideration
                  and (y) a fraction  (the "Cash  Fraction"),  the  numerator of
                  which shall be the Cash Election Number and the denominator of
                  which shall be the total  number of Cash  Election  Shares and
                  (B) a number of shares of  Valero  Common  Stock  equal to the
                  product of (x) the Exchange  Ratio and (y) a fraction equal to
                  one (1) minus the Cash Fraction.

        (h) If the aggregate  number of  Stock Election Shares exceeds the Stock
Election Number,  all Cash Election Shares and all Non-Election  Shares shall be
converted into the right to receive cash, and all Stock Election Shares shall be
converted  into  the  right  to  receive  Valero  Common  Stock  and cash in the
following manner:

                           Each Stock Election Share shall be converted into the
                  right to receive (A) a number of shares of Valero Common Stock
                  equal  to the  product  of (x) the  Exchange  Ratio  and (y) a
                  fraction (the "Stock Fraction"),  the numerator of which shall
                  be the Stock  Election  Number  and the  denominator  of which
                  shall be the total number of Stock Election Shares, and (B) an
                  amount  of  cash  (rounded  to  the  nearest  cent),   without
                  interest,  equal to the product of (x) the Cash  Consideration
                  and (y) a fraction equal to one (1) minus the Stock Fraction.

        (i) In  the event  that neither  Section 3.1(g) or 3.1(h) is applicable,
all Cash Election  Shares shall be converted  into the right to receive the Cash
Consideration,  all Stock  Election  Shares shall be converted into the right to
receive the Stock  Consideration and all Non-Election  Shares shall be converted
into the right to receive (A) an amount of cash  (rounded to the nearest  cent),
without interest,  equal to the product of (x) the Cash  Consideration and (y) a
fraction (the "Non-Election Cash Fraction"), the numerator of which shall be the
Cash Election Number less the number of Cash Election Shares and the denominator
of which shall be the number of Non-Election  Shares, and (B) a number of shares
of Valero Common Stock equal to the product of (x) the Exchange  Ratio and (y) 1
minus the Non-Election Cash Fraction.

        (j) UDS shall use all  reasonable  best  efforts to cause  copies of the
Form of Election  (which shall contain a Letter of Transmittal to be mailed with
the Joint Proxy  Statement/Prospectus  to the record holders of UDS Common Stock
(other  than  holders of  Dissenting  Shares) as of the record  date for the UDS
Stockholders  Meeting) and to make the Form of Election available to all persons
who become  record  holders of UDS Common Stock  during the period  between such
record date and the Election  Deadline.  A properly  completed  Form of Election
must be received by the Exchange  Agent by 5:00 p.m., New York City time, on the
second business day preceding the Closing Date (the "Election Deadline"),  which
day shall not be less than 20 days  after  the  initial  mailing  of the Form of
Election, in order to be effective.  An election by a holder of UDS Common Stock
shall be validly  made only if the Exchange  Agent shall have timely  received a
Form of  Election  properly  completed  and  executed  (with  the  signature  or
signatures  thereon  guaranteed  as  required by the Form of  Election)  by that
stockholder  accompanied  either  by the  UDS  Certificate  or UDS  Certificates
representing  all of the shares of UDS Common  Stock owned by that  stockholder,
duly endorsed in blank or otherwise in form acceptable for transfer on the books
of UDS, or by an appropriate  guarantee of delivery in the form customarily used
in transactions of this nature from a member of a national securities  exchange,
a  member  of  the  National  Association  of  Securities  Dealers,  Inc.,  or a
commercial  bank or trust  company in the United  States.  All  elections may be
revoked until the Election Deadline in writing by the record holders  submitting
Forms of Election.  Valero shall have the authority, in its sole discretion,  to
make all  determinations as to whether or not a Form of Election has been timely
received.

        (k)  Notwithstanding  anything  in  this  Article III  to the  contrary,
the Cash  Election  Number shall be not greater  than the  greatest  number that
would permit the satisfaction of the conditions set forth in Sections 7.2(c) and
7.3(c).

3.2 Stock  Options.  (a) Each option to purchase  UDS Common Stock (a "UDS Stock
Option") granted under UDS Stock Plans which is outstanding immediately prior to
the  Effective  Time shall cease to  represent a right to acquire  shares of UDS
Common Stock and shall be converted (as so converted, a "UDS Converted Option"),
at the Effective Time and subject to the immediately following sentence, into an
option to purchase  Valero Common Stock (a "Valero Stock  Option"),  on the same
terms and conditions as were applicable  under the UDS Stock Option.  The number
of shares of Valero  Common Stock subject to each such Valero Stock Option shall
be the number of shares of UDS  Common  Stock  subject  to the UDS Stock  Option
multiplied by the Exchange Ratio,  rounded,  if necessary,  to the nearest whole
share of Valero  Common  Stock,  and such  Valero  Stock  Option  shall  have an
exercise price per share (rounded to the nearest  one-hundredth of a cent) equal
to the per share  exercise  price  specified in such UDS Stock Option divided by
the Exchange Ratio; provided,  however, that in the case of any UDS Stock Option
to which  Section 421 of the Code as of the  Effective  Time (after  taking into
account the effect of any accelerated  vesting thereof) applies by reason of its
qualification  under Section 422 of the Code, the exercise price,  the number of
shares  subject to such option and the terms and  conditions of exercise of such
option shall be  determined  in a manner  consistent  with the  requirements  of
Section  424(a) of the Code. As of the Effective  Time,  Valero shall assume the
obligations  of UDS under the UDS Stock Plans,  and from and after the Effective
Time,  except as otherwise set forth herein,  the terms of each UDS Stock Option
and the UDS Stock Plan under which such UDS Stock Option was initially  granted,
in each  case,  as in effect  immediately  prior to the  Effective  Time,  shall
continue to apply to the corresponding Valero Stock Option.

                  (b) Prior to the Effective  Time, UDS shall take all necessary
action for the  adjustment  of UDS  Converted  Options  under this  Section 3.2.
Valero shall  reserve for issuance a number of shares of Valero  Common Stock at
least equal to the number of shares of Valero  Common Stock that will be subject
to UDS Converted Options.  As soon as practicable  following the Effective Time,
Valero shall file a registration statement on Form S-8 (or any successor,  or if
Form S-8 is not available, other appropriate,  forms) with respect to the shares
of Valero Common Stock subject to UDS Converted  Options and shall  maintain the
effectiveness  of such  registration  statement or registration  statements (and
maintain the current status of the prospectus or prospectuses contained therein)
for so long as such options remain outstanding.

3.3  Exchange  Fund.   Prior  to  the  Effective  Time,   Valero  shall  appoint
Computershare Investor Services,  LLC, or a commercial bank or trust company, or
a subsidiary  thereof,  reasonably  acceptable to UDS, to act as exchange  agent
hereunder  for the  purpose  of  exchanging  UDS  Certificates  for  the  Merger
Consideration (the "Exchange Agent").  At or prior to the Effective Time, Valero
shall  deposit with the Exchange  Agent,  in trust for the benefit of holders of
shares of UDS  Common  Stock,  (a)  certificates  representing  shares of Valero
Common Stock and (b) cash, to be issued and paid pursuant to Sections 3.1(b) and
(d) and Section 3.7 in exchange for outstanding  shares of UDS Common Stock upon
due surrender of UDS  Certificates  pursuant to this Article III.  Following the
Effective Time, Valero agrees to make available to the Exchange Agent, from time
to time as needed,  cash sufficient to pay any dividends and other distributions
pursuant to Section 3.5. Any cash and  certificates  representing  Valero Common
Stock  deposited with the Exchange Agent  (including the amount of any dividends
or  other  distributions  payable  with  respect  thereto  and  cash  in lieu of
fractional  shares to be paid  pursuant  to Section  3.7) shall  hereinafter  be
referred to as the "Exchange Fund".

3.4 Exchange  Procedures.  Promptly after the Effective Time, Valero shall cause
the Exchange Agent to mail to each holder of a UDS  Certificate  (other than UDS
Certificates  representing  Dissenting  Shares) that has not timely  submitted a
properly completed and executed Form of Election accompanied by an appropriately
endorsed  Certificate or Certificates  representing all of the shares of Company
Common Stock owned by that  shareholder  (or,  alternatively,  by an appropriate
guarantee of delivery) (a) a letter of transmittal (the "Letter of Transmittal")
that shall specify that delivery  shall be effected,  and risk of loss and title
to the UDS  Certificates  shall  pass,  only  upon  proper  delivery  of the UDS
Certificates to the Exchange Agent, and which Letter of Transmittal  shall be in
customary  form and have such other  provisions as Valero or UDS may  reasonably
specify (such letter to be reasonably  acceptable to UDS and Valero prior to the
Effective  Time) and (b)  instructions  for  effecting the surrender of such UDS
Certificates  in  exchange  for the  Merger  Consideration,  together  with  any
dividends and other  distributions  with respect thereto and any cash in lieu of
fractional  shares.  Upon  surrender of a UDS  Certificate to the Exchange Agent
together  with such Letter of  Transmittal  or the Form of Election  pursuant to
Section 3.1(j),  duly executed and completed in accordance with the instructions
thereto,  and such other documents as may reasonably be required by the Exchange
Agent,  the  holder of such UDS  Certificate  shall be  entitled  to  receive in
exchange  therefor  (i)  shares  of  Valero  Common  Stock  (which  shall  be in
uncertificated  book-entry form,  unless a physical  certificate is requested by
such  holder  or  is  otherwise   required  by  applicable  law  or  regulation)
representing,  in the aggregate, the whole number of shares that such holder has
the right to receive  pursuant to Section 3.1(b) or 3.1(d) (in each case,  after
taking into  account all shares of UDS Common  Stock then held by such  holder),
(ii) a check in the amount equal to the cash,  if any,  that such holder has the
right to receive  pursuant to Section 3.1, and (iii) a check in the amount equal
to the cash, if any,  that such holder has the right to receive  pursuant to the
provisions of this Article III other than Section 3.1, including cash in lieu of
any  fractional  shares of Valero  Common  Stock  pursuant  to  Section  3.7 and
dividends and other  distributions  pursuant to Section 3.5. No interest will be
paid or will  accrue on any cash  payable  pursuant  to the  provisions  of this
Article III. In the event of a transfer of ownership of UDS Common Stock that is
not  registered  in the  transfer  records of UDS,  one or more shares of Valero
Common Stock evidencing, in the aggregate, the proper number of shares of Valero
Common  Stock  pursuant  to Section  3.1,  a check in the proper  amount of cash
representing Cash  Consideration  pursuant to Section 3.1, a check in the proper
amount of cash in lieu of any fractional  shares of Valero Common Stock pursuant
to Section 3.7 and any dividends or other  distributions to which such holder is
entitled  pursuant to Section 3.5, may be issued with respect to such UDS Common
Stock to such a transferee if the UDS  Certificate  representing  such shares of
UDS  Common  Stock  is  presented  to the  Exchange  Agent,  accompanied  by all
documents required to evidence and effect such transfer and to evidence that any
applicable stock transfer taxes have been paid.

3.5  Distributions  with Respect to  Unexchanged  Shares.  No dividends or other
distributions  with a record date after the Effective  Time shall be paid to the
holder of any unsurrendered UDS Certificate with respect to the shares of Valero
Common  Stock that such holder  would be entitled to receive  upon  surrender of
such UDS Certificate, and no cash payment in lieu of fractional shares of Valero
Common Stock shall be paid to any such holder pursuant to Section 3.7 until such
holder shall surrender such UDS Certificate in accordance with Section 3.1(j) or
Section 3.4.  Subject to the effect of applicable  laws,  following the later of
the surrender of any such UDS Certificate and the Effective Time, there shall be
paid to the record holder  thereof  without  interest,  (a) promptly  after such
time,  the  amount of any cash  payable in lieu of  fractional  shares of Valero
Common  Stock to which such holder is  entitled  pursuant to Section 3.7 and the
amount  of  dividends  or other  distributions  with a  record  date  after  the
Effective  Time  theretofore  paid with  respect to such whole  shares of Valero
Common Stock and (b) at the appropriate payment date, the amount of dividends or
other  distributions  with a record date after the Effective  Time and a payment
date  subsequent  thereto and to such  surrender  payable  with  respect to such
shares of Valero Common Stock.

3.6 No Further Ownership Rights in UDS Common Stock. All shares of Valero Common
Stock  issued and cash paid upon  conversion  of shares of UDS  Common  Stock in
accordance  with the terms of this Article III (including any cash paid pursuant
to  Section  3.5 or 3.7)  shall be deemed  to have  been  issued or paid in full
satisfaction of all rights pertaining to the shares of UDS Common Stock.

3.7 No Fractional  Shares of Valero Common Stock.  No  certificates  or scrip or
shares of Valero Common Stock  representing  fractional  shares of Valero Common
Stock or  book-entry  credit of the same shall be issued upon the  surrender for
exchange of UDS  Certificates,  and such  fractional  share  interests  will not
entitle  the owner  thereof  to vote or to have any rights of a  stockholder  of
Valero  or a holder  of  shares  of  Valero  Common  Stock.  In lieu of any such
fractional  share, each holder of shares of UDS Common Stock who would otherwise
have  been  entitled  to a  fraction  of a share of  Valero  Common  Stock  upon
surrender  of UDS  Certificates  (determined  after  taking into account all UDS
Certificates  delivered by such holder) shall be paid upon such  surrender  cash
(without interest) in an amount equal to the value (determined with reference to
the  closing  price of a share of Valero  Common  Stock as  reported on the NYSE
Composite  Tape on the last full  trading day  immediately  prior to the Closing
Date) of such  fractional  interest.  Such payment  with  respect to  fractional
shares is merely intended to provide a mechanical  rounding off of, and is not a
separately bargained for, consideration.

3.8  Termination of Exchange Fund. Any portion of the Exchange Fund that remains
undistributed  to the holders of UDS  Certificates  one year after the Effective
Time shall,  at Valero's  request,  be  delivered  to Valero or otherwise on the
instruction  of  Valero,  and any  holders  of UDS  Certificates  who  have  not
theretofore  complied  with this Article III shall after such delivery look only
to Valero for the Merger  Consideration with respect to the shares of UDS Common
Stock formerly  represented  thereby to which such holders are entitled pursuant
to Sections 3.1 and 3.4, any cash in lieu of fractional  shares of Valero Common
Stock to which  such  holders  are  entitled  pursuant  to  Section  3.7 and any
dividends  or  distributions  with  respect to shares of Valero  Common Stock to
which such holders are entitled pursuant to Section 3.5. Any such portion of the
Exchange  Fund  remaining  unclaimed  by holders  of shares of UDS Common  Stock
immediately  prior to such time as such amounts  would  otherwise  escheat to or
become property of any  Governmental  Entity shall,  to the extent  permitted by
law,  become the  property of Valero free and clear of any claims or interest of
any Person previously entitled thereto.

3.9 No Liability.  None of Valero,  UDS or the Exchange Agent shall be liable to
any  Person in  respect  of any  Merger  Consideration  from the  Exchange  Fund
delivered to a public official  pursuant to any applicable  abandoned  property,
escheat or similar law.

3.10  Investment of the Exchange  Fund. The Exchange Agent shall invest any cash
included in the Exchange  Fund as directed by Valero on a daily basis;  provided
that no such  investment or loss thereon shall affect the amounts payable or the
timing  of  the  amounts  payable  to UDS  stockholders  pursuant  to the  other
provisions  of this Article III.  Any interest and other income  resulting  from
such investments shall promptly be paid to Valero.

3.11 Lost  Certificates.  If any UDS Certificate (other than any UDS Certificate
representing Dissenting Shares) shall have been lost, stolen or destroyed,  upon
the  making  of an  affidavit  of that  fact by the  Person  claiming  such  UDS
Certificate  to be lost,  stolen or  destroyed  and, if required by Valero,  the
posting by such Person of a bond in such reasonable  amount as Valero may direct
as indemnity  against any claim that may be made against it with respect to such
UDS Certificate, following the Effective Time the Exchange Agent will deliver in
exchange  for  such  lost,  stolen  or  destroyed  UDS  Certificate  the  Merger
Consideration   with  respect  to  the  shares  of  UDS  Common  Stock  formerly
represented  thereby,  any cash in lieu of  fractional  shares of Valero  Common
Stock, and unpaid  dividends and  distributions on shares of Valero Common Stock
deliverable in respect thereof, pursuant to this Agreement.

3.12  Withholding  Rights.  Valero shall be entitled to deduct and withhold from
the  consideration  otherwise payable pursuant to this Agreement such amounts as
it is required to deduct and withhold with respect to the making of such payment
under the Code and the  rules and  regulations  promulgated  thereunder,  or any
provision of state,  local or foreign Tax law. To the extent that amounts are so
withheld or paid over to or deposited with the relevant  Governmental  Entity by
Valero,  such  amounts  shall be treated for all  purposes of this  Agreement as
having  been  paid  to the  Person  in  respect  of  which  such  deduction  and
withholding was made by Valero.

3.13  Further  Assurances.  At and after the  Effective  Time,  the officers and
directors  of the  Surviving  Corporation  shall be  authorized  to execute  and
deliver,  in the name and on behalf of the  Surviving  Corporation  or UDS,  any
deeds, bills of sale,  assignments or assurances and to take and do, in the name
and on behalf of the Surviving  Corporation or UDS, any other actions and things
necessary to vest,  perfect or confirm of record or  otherwise in the  Surviving
Corporation  any and all right,  title and  interest in, to and under any of the
rights,  properties  or  assets  acquired  or to be  acquired  by the  Surviving
Corporation as a result of, or in connection with, the Merger.

3.14  Stock  Transfer  Books.  The stock  transfer  books of UDS shall be closed
immediately upon the Effective Time, and there shall be no further  registration
of transfers of shares of UDS Common Stock  thereafter on the records of UDS. On
or after the  Effective  Time,  any UDS  Certificates  presented to the Exchange
Agent,  Valero or the  Surviving  Corporation  for any reason shall be converted
into the right to receive the Merger Consideration with respect to the shares of
UDS Common Stock  formerly  represented  thereby  (including any cash in lieu of
fractional  shares  of Valero  Common  Stock to which the  holders  thereof  are
entitled  pursuant to Section 3.7 and any  dividends or other  distributions  to
which the holders thereof are entitled pursuant to Section 3.5).

                                   ARTICLE IV
                         REPRESENTATIONS AND WARRANTIES

4.1  Representations  and Warranties of UDS. Except as disclosed in a section of
the UDS disclosure schedule delivered to Valero concurrently  herewith (the "UDS
Disclosure  Schedule")  corresponding  to the  subsection of this Section 4.1 to
which such disclosure  applies,  UDS hereby represents and warrants to Valero as
follows:

        (a) Corporate  Organization.  (i) UDS is  a corporation  duly organized,
validly  existing and in good standing  under the laws of the State of Delaware.
UDS has the corporate  power and authority to own or lease all of its properties
and assets and to carry on its  business  as it is now being  conducted,  and is
duly  licensed or  qualified  to do business in each  jurisdiction  in which the
nature of the  business  conducted  by it or the  character  or  location of the
properties   and  assets  owned  or  leased  by  it  makes  such   licensing  or
qualification necessary, except where the failure to be so licensed or qualified
would not,  either  individually  or in the aggregate,  have a Material  Adverse
Effect on UDS. True and complete copies of the Certificate of Incorporation  and
the  By-Laws  of UDS,  as in  effect  as of the  date of  this  Agreement,  have
previously been made available by UDS to Valero.

                           (ii) Each Subsidiary of UDS (A) is duly organized and
                  validly  existing  under  the  laws  of  its  jurisdiction  of
                  organization, (B) is duly qualified to do business and in good
                  standing in all jurisdictions  (whether federal,  state, local
                  or foreign)  where its ownership or leasing of property or the
                  conduct of its business  requires it to be so qualified and in
                  which the  failure  to be so  qualified  would have a Material
                  Adverse  Effect on UDS,  and (C) has all  requisite  corporate
                  power and authority to own or lease its  properties and assets
                  and to carry on its business as now conducted.

        (b)  Capitalization.  (i) The authorized  capital  stock of UDS consists
of (A)  250,000,000  shares of UDS Common Stock (each of which  includes one UDS
Right),  of  which,  as of  May 1,  2001,  71,524,496  shares  were  issued  and
outstanding,  2,234,812 shares were held in the GSOP and 17,116,837  shares were
held in treasury and (B) 25,000,000  shares of preferred  stock, par value $0.01
per share,  of UDS ("UDS Preferred  Stock,"  together with the UDS Common Stock,
the "UDS Capital Stock"),  of which no shares are issued and  outstanding.  From
May 1, 2001 to the date of this  Agreement,  no shares of UDS Capital Stock have
been  issued  except  pursuant to employee  and  director  stock plans of UDS in
effect as of the date hereof  (the "UDS Stock  Plans").  Except  pursuant to the
terms of options,  stock and restricted units issued pursuant to UDS Stock Plans
and  outstanding  as of the  date  hereof  or  issued  thereafter  as  expressly
permitted hereby,  and pursuant to the UDS Rights,  UDS does not have and is not
bound by any outstanding subscriptions, options, warrants, calls, commitments or
agreements of any  character  calling for the purchase or issuance of any shares
of UDS Capital Stock or any other equity  securities of UDS or any securities of
UDS  representing  the right to purchase or otherwise  receive any shares of UDS
Capital  Stock.  As of May 1, 2001, no shares of UDS Capital Stock were reserved
for  issuance,  except for  12,525,465  shares of UDS Common Stock  reserved for
issuance upon the exercise of stock options  pursuant to the UDS Stock Plans and
in respect of the  employee  and  director  savings,  compensation  and deferred
compensation  plans  described in the UDS 2000 10-K, and no shares of UDS Common
Stock reserved for issuance in connection with the UDS Rights Agreement. UDS has
no Voting Debt issued or outstanding.

                           (ii)  Except for  immaterial  amounts  of  directors'
                  qualifying  shares in foreign  Subsidiaries  of UDS, UDS owns,
                  directly  or  indirectly,  all of the issued  and  outstanding
                  shares of capital stock or other equity ownership interests of
                  each Subsidiary of UDS, free and clear of any liens,  pledges,
                  charges,   encumbrances  and  security  interests   whatsoever
                  ("Liens"),   and  all  of  such  shares  or  equity  ownership
                  interests are duly authorized and validly issued and are fully
                  paid,  nonassessable  and free of preemptive  rights,  with no
                  personal  liability  attaching to the  ownership  thereof.  No
                  Subsidiary  of  UDS  has  or  is  bound  by  any   outstanding
                  subscriptions,   options,   warrants,  calls,  commitments  or
                  agreements  of any  character  calling  for  the  purchase  or
                  issuance  of any shares of capital  stock or any other  equity
                  security of such Subsidiary or any securities representing the
                  right to purchase or  otherwise  receive any shares of capital
                  stock or any other equity security of such Subsidiary. Section
                  4.2(b)(ii) of the UDS Disclosure Schedule sets forth a list of
                  each  material  investment  of UDS in any  corporation,  joint
                  venture,  partnership,  limited  liability  company  or  other
                  entity other than its  Subsidiaries,  which,  individually  or
                  taken  together  in  the  aggregate,  would  be  considered  a
                  Significant  Subsidiary if such investment constituted control
                  of such entity (each a "Non-Subsidiary Affiliate").

(c) Authority;  No Violation.  (i) UDS has full corporate power and authority to
execute  and  deliver  this  Agreement  and  to  consummate   the   transactions
contemplated  hereby.  The  execution  and  delivery of this  Agreement  and the
consummation of the transactions  contemplated hereby have been duly and validly
approved by the Board of  Directors  of UDS.  The Board of  Directors of UDS has
directed that this Agreement be submitted to UDS  stockholders for approval at a
meeting of UDS  stockholders  for the purpose of  approving  the Merger and this
Agreement (the "UDS Stockholders Meeting"),  and, except for the approval of the
Merger  and of  this  Agreement  by the  affirmative  vote of the  holders  of a
majority of the  outstanding  shares of UDS Common  Stock (the "UDS  Stockholder
Approval"),  no other corporate  proceedings on the part of UDS are necessary to
approve this Agreement and to consummate the transactions  contemplated  hereby.
This  Agreement  has been duly and validly  executed  and  delivered  by UDS and
(assuming due  authorization,  execution  and delivery by Valero)  constitutes a
valid and binding obligation of UDS,  enforceable against UDS in accordance with
its terms.

                           (ii)  Neither  the  execution  and  delivery  of this
                  Agreement  by  UDS,  nor  the   consummation  by  UDS  of  the
                  transactions  contemplated  hereby, nor compliance by UDS with
                  any of the terms or  provisions  hereof,  will (A) violate any
                  provision of the  Certificate of  Incorporation  or By-Laws of
                  UDS,  each as amended,  or (B) assuming  that the consents and
                  approvals referred to in Section 4.1(d) are duly obtained, (x)
                  violate  any  statute,  code,  ordinance,   rule,  regulation,
                  judgment, order, writ, decree or injunction applicable to UDS,
                  any of its Subsidiaries or Non-Subsidiary Affiliates or any of
                  their respective properties or assets or (y) violate, conflict
                  with,  result in a breach of any  provision  of or the loss of
                  any benefit  under,  constitute  a default (or an event which,
                  with  notice or lapse of time,  or both,  would  constitute  a
                  default)  under,  result in the  termination  of or a right of
                  termination or cancellation under,  accelerate the performance
                  required by,  accelerate any right or benefit  provided by, or
                  result in the creation of any Lien upon any of the  respective
                  properties  or assets of UDS, any of its  Subsidiaries  or its
                  Non-Subsidiary  Affiliates under, any of the terms, conditions
                  or provisions of any note, bond, mortgage,  indenture, deed of
                  trust,  license,  lease,  agreement  or  other  instrument  or
                  obligation   to  which  UDS,  any  of  its   Subsidiaries   or
                  Non-Subsidiary  Affiliates is a party, or by which they or any
                  of  their  respective  properties  or  assets  may be bound or
                  affected, except (in the case of clause (B)(y) above) for such
                  violations,  conflicts,  breaches  or  defaults  which  either
                  individually  or in the  aggregate  will not  have a  Material
                  Adverse Effect on UDS or the Surviving Corporation.

(d)  Consents and  Approvals.  Except for (i) the filing of a  notification  and
report form under the HSR Act and the  termination  or expiration of the waiting
period under the HSR Act, (ii) the filing of any other required  applications or
notices with any state or foreign agencies and approval of such applications and
notices (the "Other Approvals"),  (iii) the filing with the SEC of a joint proxy
statement/prospectus  relating  to  the  matters  to be  submitted  to  Valero's
stockholders at the Valero Stockholders  Meeting and the matters to be submitted
to  UDS's  stockholders  at the  UDS  Stockholders  Meeting  (such  joint  proxy
statement/prospectus,  and any  amendments or  supplements  thereto,  the "Joint
Proxy  Statement/Prospectus")  and a  registration  statement  on Form  S-4 with
respect to the issuance of Valero Common Stock in the Merger (such Form S-4, and
any amendments or supplements  thereto,  the "Form S-4"), (iv) the filing of the
Certificate of Merger, (v) any consents,  authorizations,  approvals, filings or
exemptions in connection  with  compliance with the rules of the NYSE, (vi) such
filings  and  approvals  as are  required  to be  made  or  obtained  under  the
securities or "Blue Sky" laws of various states in connection  with the issuance
of Valero Common Stock  pursuant to this  Agreement  (the  consents,  approvals,
filings and registration  required under or in relation to the foregoing clauses
(ii) though (vi) being referred to as "Necessary Consents") and (vii) such other
consents, approvals, filings and registrations the failure of which to obtain or
make would not  reasonably be expected to have a Material  Adverse Effect on UDS
or the  Surviving  Corporation,  no  consents  or  approvals  of or  filings  or
registrations  with any  supranational,  national,  state,  municipal,  local or
foreign government,  any  instrumentality,  subdivision,  court,  administrative
agency or commission or other authority thereof,  or any  quasi-governmental  or
private body exercising any regulatory,  taxing, importing or other governmental
or quasi-governmental authority (each, a "Governmental Entity") are necessary in
connection  with (A) the execution and delivery by UDS of this Agreement and (B)
the consummation by UDS of the transactions contemplated by this Agreement.

(e)  Financial  Reports  and SEC  Documents.  The UDS 2000  10-K  and all  other
reports,  registration  statements,  definitive  proxy statements or information
statements filed or to be filed by UDS or any of its Subsidiaries  subsequent to
December 31, 1998 under the Securities Act or under Sections  13(a),  13(c),  14
and 15(d) of the Exchange Act in the form filed,  or to be filed  (collectively,
the "UDS SEC  Documents"),  with the SEC,  (i)  complied  or will  comply in all
material  respects  as to  form  with  the  applicable  requirements  under  the
Securities  Act or the  Exchange  Act,  as the case  may be,  and (ii) as of its
filing date, did not or will not contain any untrue statement of a material fact
or omit to state a material fact  required to be stated  therein or necessary to
make the statements made therein, in light of the circumstances under which they
were made,  not  misleading;  and each of the  balance  sheets  contained  in or
incorporated by reference into any such UDS SEC Document  (including the related
notes  and  schedules  thereto)  fairly  presents  or will  fairly  present  the
financial position of the entity or entities to which it relates as of its date,
and each of the statements of operations and changes in stockholders' equity and
cash flows or equivalent  statements in such UDS SEC  Documents  (including  any
related notes and schedules  thereto) fairly presents or will fairly present the
results of  operations,  changes  in  stockholders'  equity and  changes in cash
flows, as the case may be, of the entity or entities to which it relates for the
periods to which it relates,  in each case in accordance with GAAP  consistently
applied  during the  periods  involved,  except,  in each case,  as may be noted
therein,  subject to normal year-end audit  adjustments in the case of unaudited
statements.

(f)  Absence of  Undisclosed  Liabilities.  Except as  disclosed  in the audited
financial  statements (or notes thereto) included in the UDS 2000 10-K,  neither
UDS nor any of its  Subsidiaries had at December 31, 2000, or has incurred since
that date through the date  hereof,  any  liabilities  or  obligations  (whether
absolute,   accrued,   contingent  or  otherwise)  of  any  nature,  except  (a)
liabilities,  obligations  or  contingencies  which (i) are  accrued or reserved
against in the  financial  statements  in the UDS 2000 10-K or  reflected in the
notes  thereto or (ii) were  incurred in the  ordinary  course of  business  and
consistent with past practices,  (b)  liabilities,  obligations or contingencies
which (i) would not reasonably be expected, individually or in the aggregate, to
have a Material  Adverse Effect on UDS, or (ii) have been  discharged or paid in
full  prior  to  the  date  hereof,   and  (c)   liabilities,   obligations  and
contingencies  which  are  of a  nature  not  required  to be  reflected  in the
consolidated  financial  statements  of UDS and  its  Subsidiaries  prepared  in
accordance with GAAP consistently applied.

(g) Absence of Certain Changes or Events. (i) Since December 31, 2000, except as
set forth in UDS SEC  Documents  filed since  December 31, 2000 and prior to the
date hereof,  no event or events have occurred that has had or would  reasonably
be expected to have, either individually or in the aggregate, a Material Adverse
Effect on UDS.

             (ii) Since  December 31, 2000, UDS and its  Subsidiaries  have
                  carried  on  their  respective   businesses  in  all  material
                  respects in the ordinary course.

            (iii) Since   December  31,  2000,  neither  UDS  nor  any   of  its
                  Subsidiaries  has (A)  except for such  actions as were in the
                  ordinary  course  of business consistent with past practice or
                  except as required by applicable law, (I) increased the wages,
                  salaries,  compensation,  pension, or other fringe benefits or
                  perquisites payable to any executive officer or  director from
                  the  amount thereof in effect as of December 31, 2000, or (II)
                  granted  any  severance  or  termination pay, entered into any
                  contract to make or grant any severance or termination pay, or
                  paid any bonuses, to any executive  officer or director or (B)
                  suffered  any  strike, work stoppage, slowdown, or other labor
                  disturbance which would be reasonably be expected to have, (in
                  the case of clause (A) or (B) above) either individually or in
                  the aggregate, a Material Adverse Effect on UDS.

(iv) Since  December 31, 2000,  UDS has not declared any dividends on UDS Common
Stock other than its regular quarterly dividends.

(h) Legal  Proceedings.  There is no suit, action or proceeding or investigation
pending or, to the knowledge of UDS, threatened, against or affecting UDS or any
of its Subsidiaries that would, individually or in the aggregate,  reasonably be
expected to have a Material  Adverse  Effect on UDS, nor is there any  judgment,
decree,  injunction,  rule or order of any  Governmental  Entity  or  arbitrator
outstanding against UDS or its Subsidiaries having, or which would reasonably be
expected to have, individually or in the aggregate, any such effect.

(i) Compliance with Applicable  Law. UDS and each of its  Subsidiaries  hold all
licenses,  franchises,  permits  and  authorizations  necessary  for the  lawful
conduct of their  respective  businesses  under and  pursuant to each,  and have
complied in all respects with and are not in default under any,  applicable law,
statute, order, rule or regulation of any Governmental Entity relating to UDS or
any of its  Subsidiaries,  except  where  the  failure  to  hold  such  license,
franchise,  permit or authorization or such  noncompliance or default would not,
either  individually  or in the  aggregate,  reasonably  be  expected  to have a
Material Adverse Effect on UDS.

(j)  Contracts.  (i)  Neither UDS nor any of its  Subsidiaries  is a party to or
bound by any contract, arrangement, commitment or understanding (whether written
or oral) (A) with  respect  to the  employment  of any  directors,  officers  or
employees  other than in the ordinary  course of business  consistent  with past
practice,  (B) which,  upon the  consummation  or  stockholder  approval  of the
transactions  contemplated  by this  Agreement,  will (either  alone or upon the
occurrence of any additional  acts or events) result in any payment  (whether of
severance  pay or  otherwise)  becoming  due from  Valero,  UDS,  the  Surviving
Corporation or any of their  respective  Subsidiaries to any director officer or
employee thereof, (C) which is a "material contract" (as such term is defined in
Item  601(b)(10) of Regulation S-K of the SEC) to be performed after the date of
this Agreement that has not been filed or  incorporated  by reference in the UDS
SEC Documents filed prior to the date hereof, or (D) which materially  restricts
the conduct of any line of business  by UDS or upon  consummation  of the Merger
will materially  restrict the ability of Valero or the Surviving  Corporation to
engage  in any line of  business.  Each  contract,  arrangement,  commitment  or
understanding  of the type described in this Section 4.1(j),  whether or not set
forth in the UDS Disclosure  Schedule or in such UDS SEC Documents,  is referred
to herein as a "UDS Contract".

                           (ii) (A) Each UDS  Contract  is valid and  binding on
                  UDS and any of its  Subsidiaries  that is a party thereto,  as
                  applicable,  and in full force and effect, (B) UDS and each of
                  its  Subsidiaries has in all material  respects  performed all
                  obligations  required to be performed by it to date under each
                  UDS  Contract,   except  where  such   noncompliance,   either
                  individually  or in the  aggregate,  would not  reasonably  be
                  expected  to have a Material  Adverse  Effect on UDS,  and (C)
                  neither  UDS  nor any of its  Subsidiaries  knows  of,  or has
                  received  notice of, the  existence  of any event or condition
                  which constitutes,  or, after notice or lapse of time or both,
                  will constitute,  a material default on the part of UDS or any
                  of its Subsidiaries under any such UDS Contract,  except where
                  such default,  either individually or in the aggregate,  would
                  not  reasonably be expected to have a Material  Adverse Effect
                  on UDS.

(k) Environmental  Liability.  There are no legal,  administrative,  arbitral or
other proceedings,  claims,  actions,  causes of action,  private  environmental
investigations or remediation  activities or governmental  investigations of any
nature seeking to impose,  or that could reasonably result in the imposition of,
on UDS, any liability or obligation arising under common law or under any local,
state or  federal  environmental  statute,  regulation  or  ordinance  including
CERCLA,  pending or  threatened  in writing  against  UDS,  which  liability  or
obligation,  either  individually  or in  the  aggregate,  would  reasonably  be
expected  to have a Material  Adverse  Effect on UDS.  UDS is not subject to any
agreement,  order, judgment,  decree, letter or memorandum by or with any court,
governmental authority,  regulatory agency or third party imposing any liability
or obligation with respect to the foregoing that, either  individually or in the
aggregate,  would  reasonably be expected to have a Material  Adverse  Effect on
UDS.

(l) Employee  Benefit  Plans;  Labor  Matters. (i)  Section 4.1(l)(i) of the UDS
Disclosure Schedule includes a complete list of all UDS Benefit Plans.

         (ii)     With  respect  to  each  UDS  Plan,  UDS has delivered or made
                  available to Valero a true, correct and complete copy of:  (A)
                  each UDS Plan document or a summary of any unwritten UDS Plan,
                  trust  agreement  and  insurance  contract  or  other  funding
                  vehicle; (B)  the most recent Annual Report (Form 5500 Series)
                  and  accompanying  schedule,  if  any; (C) the current summary
                  plan  description  and  any  material  modifications  thereto,
                  if any (in each case, whether or not  required to be furnished
                  under ERISA); (D) the  most recent annual financial report, if
                  any; (E)  the  most  recent actuarial report, if any; and (vi)
                  the most recent determination letter from the Internal Revenue
                  Service, if any.  Except as specifically provided in the fore-
                  going  documents  delivered or made available to Valero, there
                  are  no  amendments  to any UDS Plan that have been adopted or
                  approved  nor has UDS or any of its Subsidiaries undertaken to
                  make  any  such  amendments or to adopt or approve any new UDS
                  Plan.

        (iii)     Section  4.1(l)(iii) of the UDS Disclosure Schedule identifies
                  each UDS Plan that is intended to be a "qualified plan" within
                  the  meaning  of Section  401(a) of the Code  ("UDS  Qualified
                  Plans").  The Internal  Revenue Service has issued a favorable
                  determination  letter with respect to each UDS Qualified  Plan
                  and the related trust, and such  determination  letter has not
                  been  revoked.  No  circumstances  exist  and no  events  have
                  occurred that could adversely  affect the qualified  status of
                  any UDS Qualified Plan or the related  trust,  which could not
                  be corrected  under the Internal  Revenue  Service's  Employee
                  Plans Compliance Resolution System (Revenue Procedure 2001-17)
                  without  material  liability.  No UDS Plan is intended to meet
                  the requirements of Code Section 501(c)(9).

         (iv)     All  contributions  required  to be made  to any  UDS  Plan by
                  applicable  law or regulation or by any plan document or other
                  contractual undertaking,  and all premiums due or payable with
                  respect to insurance  policies  funding any UDS Plan,  for any
                  period through the date hereof have been timely made.

          (v)      With respect to each UDS  Plan that is subject to Title IV or
                  Section  302  of ERISA or Section 412 or 4971 of the Code: (A)
                  there does not exist any accumulated funding deficiency within
                  the  meaning  of  Section  412  of  the Code or Section 302 of
                  ERISA, whether or not waived; (B) the fair market value of the
                  assets  of  such  UDS  Plan  equals  or  exceeds the actuarial
                  present  value  of  all  accrued  benefits under such UDS Plan
                  (whether or not vested) on an accumulated  benefits obligation
                  basis  based on the most recent actuarial report for each such
                  plan;  (C)  no  reportable event within the meaning of Section
                  4043(c)  of ERISA  for which the 30-day notice requirement has
                  not  been  waived  has  occurred,  and the consummation of the
                  transactions contemplated by this Agreement will not result in
                  the occurrence of  any such reportable event; (D) all premiums
                  to  the Pension Benefit Guaranty Corporation (the "PBGC") have
                  been  timely  paid  in  full; (E) no liability (other than for
                  premiums  to  the PBGC) under Title IV of ERISA has been or is
                  expected to be incurred by UDS or any of its Subsidiaries; and
                  (F) the PBGC has not instituted proceedings to  terminate  any
                  such  UDS  Plan  and,  to UDS's knowledge, no condition exists
                  that presents a risk that such proceedings  will be instituted
                  or  which would constitute grounds under Section 4042 of ERISA
                  for  the  termination  of,  or the appointment of a trustee to
                  administer, any such UDS Plan.

         (vi)     (A) No UDS Benefit Plan is a Multiemployer Plan or a plan that
                  has two or more contributing sponsors at least two of whom are
                  not under common  control,  within the meaning of Section 4063
                  of ERISA (a "Multiple Employer Plan"); and (B) none of UDS and
                  its  Subsidiaries  nor any ERISA  Affiliates  has incurred any
                  Withdrawal Liability that has not been satisfied in full. With
                  respect to each UDS Benefit Plan that is a Multiemployer Plan,
                  none of UDS and its Subsidiaries,  nor any of their respective
                  ERISA  Affiliates has received any  notification,  nor has any
                  reason  to  believe,  that any such  Multiemployer  Plan is in
                  reorganization,  has been  terminated,  is  insolvent,  or may
                  reasonably  be  expected  to  be  in  reorganization,   to  be
                  insolvent, or to be terminated.

        (vii)     Except as would not reasonably be expected, individually or in
                  the  aggregate,  to have a Material Adverse Effect on UDS, (A)
                  each of the UDS Plans  has  been  operated and administered in
                  all  material  respects in accordance with applicable law  and
                  administrative  rules  and  regulations  of  any  Governmental
                  Entity, including, but not limited to, ERISA and the Code, and
                  (B)  there  are  no  pending  or threatened claims (other than
                  claims  for  benefits  in  the  ordinary  course), lawsuits or
                  arbitrations  which  have  been asserted or instituted against
                  the  UDS  Plans, any fiduciaries thereof with respect to their
                  duties  to  the  UDS  Plans or the assets of any of the trusts
                  under any of the UDS Plans which could  reasonably be expected
                  to  result  in  any  material  liability  of UDS or any of its
                  Subsidiaries to the PBGC, the U.S. Department of the Treasury,
                  the U.S. Department of Labor, any UDS Plan, any participant in
                  a UDS Plan, or any other party.

       (viii)     UDS and its Subsidiaries  have no liability for life,  health,
                  medical  or other  welfare  benefits  to former  employees  or
                  beneficiaries  or  dependents   thereof,   except  for  health
                  continuation coverage as required by Section 4980B of the Code
                  or Part 6 of Title I of ERISA and at no expense to UDS and its
                  Subsidiaries.  To the  knowledge  of UDS,  UDS and each of its
                  Subsidiaries  has  reserved  the right to amend,  terminate or
                  modify at any time all  plans or  arrangements  providing  for
                  retiree health or life insurance coverage.

         (ix)     Section 4.1(l)(ix) of  the UDS Disclosure Schedule sets  forth
                  (A) an accurate and complete list of each UDS Plan under which
                  the  execution and delivery of this Agreement or the consumma-
                  tion  of  the  transactions  contemplated hereby could (either
                  alone  or  in  conjunction  with  any other event), result in,
                  cause  the  accelerated  vesting,  funding  or delivery of, or
                  increase  the  amount  or  value  of,  any  payment or benefit
                  (including the  forgiveness  of indebtedness) to any employee,
                  officer  or  director  of  UDS  or any of its Subsidiaries, or
                  could  limit  the  right  of UDS or any of its Subsidiaries to
                  amend,  merge, terminate or receive a reversion of assets from
                  any  UDS  Plan  or  related  trust  or any material employment
                  agreement  or  related  trust,  (B)  a  reasonable  good faith
                  estimate of the maximum amount of the  severance benefits that
                  could become payable to  officers and senior management of UDS
                  if their employment were terminated at the Effective Time, and
                  (C)  a reasonable good faith estimate of the maximum amount of
                  the "excess parachute payments"  within the meaning of Section
                  280G  of  the  Code  that  could become payable by UDS and its
                  Subsidiaries in connection with  the execution and delivery of
                  this  Agreement  and  the  consummation  of  the  transactions
                  contemplated hereby.

          (x)     Except as would not reasonably be expected, individually or in
                  the aggregate,  to have a Material  Adverse Effect on UDS, all
                  UDS  Benefit  Plans  subject  to the laws of any  jurisdiction
                  outside  of the  United  States  (A) have been  maintained  in
                  accordance with all applicable  requirements;  (B) if they are
                  intended  to  qualify  for  special  tax  treatment  meet  all
                  requirements for such treatment;  and (C) if they are intended
                  to be funded and/or book-reserved are fully funded and/or book
                  reserved,  as  appropriate,  based upon  reasonable  actuarial
                  assumptions.

(xi)              With  respect  to any UDS  Benefit  Plan that is an  "employee
                  stock ownership plan" within the meaning of Section 4975(e)(7)
                  of the Code (an  "ESOP"),  (A) each loan under  which the ESOP
                  was a borrower (each, a "Loan") has been fully repaid, and (B)
                  all of the securities of UDS that were acquired with such Loan
                  have been released from the pledge made in connection with the
                  Loan and fully  allocated to the accounts of  participants  in
                  the ESOP in  accordance  with  the  requirements  of  Treasury
                  Regulations Sections 54.4975-7 and 54.4975-11.

(m) Intellectual Property.  Except as would not reasonably be expected to have a
Material  Adverse  Effect  on UDS,  (i) UDS and  its  Subsidiaries  own,  or are
licensed to use, all Intellectual Property used in and necessary for the conduct
of their  business as it is currently  conducted,  (ii) to the knowledge of UDS,
the use of Intellectual  Property by UDS and its Subsidiaries  does not infringe
on or otherwise  violate the rights of any third party,  and, to the extent such
Intellectual  Property is  licensed,  its use is in  accordance  in all material
respects with the applicable license pursuant to which UDS acquired the right to
use such Intellectual Property, (iii) to the knowledge of UDS, no third party is
challenging,  infringing  on or  otherwise  violating  any  right  of UDS in the
Intellectual Property, (iv) neither UDS nor any of its Subsidiaries has received
any written notice of any pending claim, order or proceeding with respect to any
Intellectual  Property  used in and  necessary  for the conduct of UDS's and its
Subsidiaries' business as it is currently conducted, and (v) to the knowledge of
UDS,  no  Intellectual  Property  is  being  used  or  enforced  by  UDS  or its
Subsidiaries  in a manner  that would  reasonably  be  expected to result in the
abandonment,  cancellation or unenforceability of any Intellectual Property used
in and necessary for the conduct of UDS's and its  Subsidiaries'  business as it
is currently conducted.

(n) State  Takeover  Laws;  Rights  Plan.  (i) The Board of Directors of UDS has
approved this Agreement and the  transactions  contemplated by this Agreement as
required under Section 203 of the DGCL and any other  applicable  state takeover
laws and any applicable  provision of the UDS  Certificate of  Incorporation  so
that any such state  takeover  laws and such  provisions  will not apply to this
Agreement or any of the transactions contemplated hereby.

                           (ii) UDS has taken all action,  if any,  necessary or
                  appropriate so that the entering into of this  Agreement,  and
                  the consummation of the transactions  contemplated  hereby, do
                  not and  will not  result  in the  ability  of any  person  to
                  exercise  any UDS  Rights  under the UDS Rights  Agreement  or
                  enable or require the UDS Rights to  separate  from the shares
                  of UDS  Common  Stock to  which  they  are  attached  or to be
                  triggered or become  exercisable.  No  "Distribution  Date" or
                  "Stock Acquisition Date" (as such terms are defined in the UDS
                  Rights Agreement) has occurred.

(o)  Opinion of  Financial  Advisor.  UDS has  received  the  opinion of Banc of
America  Securities  LLC,  dated the date hereof,  to the effect that the Merger
Consideration  to be  received  by holders of UDS Common  Stock in the Merger is
fair to such stockholders from a financial point of view.

(p) Board Approval.  The Board of Directors of UDS, at a meeting duly called and
held, has by unanimous vote of those directors  present (i) determined that this
Agreement and the transactions contemplated hereby are advisable, fair to and in
the best  interests of the  stockholders  of UDS, (ii) approved and adopted this
Agreement  and  (iii)  recommended  that the plan of  merger  contained  in this
Agreement be adopted by the holders of UDS Common Stock.

(q)  Broker's  Fees.  Neither UDS nor any of its  Subsidiaries  nor any of their
respective  officers or directors  has employed any broker or finder or incurred
any liability for any broker's fees,  commissions or finder's fees in connection
with the transactions contemplated by this Agreement,  excluding fees to be paid
to Banc of America Securities LLC.

(r) Taxes.  (i) Except as would not reasonably be expected,  individually  or in
the aggregate, to have a Material Adverse Effect on UDS, (A) each of UDS and its
Subsidiaries  has duly and timely filed all Tax Returns  required to be filed by
it, and all such Tax Returns are true,  complete and  accurate in all  respects;
(B) UDS and each of its  Subsidiaries  has paid all Taxes required to be paid by
it, and has paid all Taxes that it was required to withhold  from amounts  owing
to any  employee,  creditor or third party;  (C) there are no pending or, to the
knowledge of UDS, threatened audits, examinations, investigations, deficiencies,
claims  or  other  proceedings  in  respect  of  Taxes  relating  to  UDS or any
Subsidiary  of UDS;  (D) there are no liens for Taxes  upon the assets of UDS or
any  Subsidiary of UDS, other than liens for current Taxes not yet due and liens
for Taxes that are being contested in good faith by appropriate proceedings; (E)
neither UDS nor any of its  Subsidiaries  has  requested  any  extension of time
within  which to file any Tax Returns in respect of any taxable  year which have
not subsequently been filed when due (pursuant to such extension),  nor provided
or been  requested  to provide  any waivers of the time to assess any Taxes that
are pending or outstanding;  (F) the consolidated  federal income Tax Returns of
UDS have been examined,  or the statute of limitations has closed,  with respect
to all taxable years through and including  1994; (G) neither UDS nor any of its
Subsidiaries  has any  liability for Taxes of any Person (other than UDS and its
Subsidiaries)  under  Treasury  Regulation  Section  1.1502-6 (or any comparable
provision  of  state,  local  or  foreign  law);  and  (H)  neither  UDS nor any
Subsidiary  of UDS is a party to any  agreement  (with any Person other than UDS
and/or any of its  Subsidiaries)  relating to the allocation or sharing of Taxes
which is currently in force.

                           (ii) UDS has not  constituted  either a "distributing
                  corporation" or a "controlled  corporation" within the meaning
                  of Section 355(a)(1)(A) of the Code in a distribution of stock
                  intended to qualify  under  Section  355(a) of the Code (i) in
                  the two  years  prior to the date of this  Agreement  (or will
                  constitute  such a  corporation  in the two years prior to the
                  Closing  Date)  or  (ii)  in a  distribution  which  otherwise
                  constitutes   part  of  a  "plan"  or   "series   of   related
                  transactions" within the meaning of Section 355(e) of the Code
                  in conjunction with the Merger.

(s) Reorganization under the Code. As of the date of this Agreement, neither UDS
nor any of its  Subsidiaries  has taken any  action or knows of any fact that is
reasonably  likely to prevent the Merger from  qualifying as a  "reorganization"
within the meaning of Section 368(a) of the Code.

(t) Form S-4; Joint Proxy  Statement/Prospectus.  None of the  information to be
supplied  by  UDS or  its  Subsidiaries  in the  Form  S-4  or the  Joint  Proxy
Statement/Prospectus  will,  at the  time  of the  mailing  of the  Joint  Proxy
Statement/Prospectus  and any amendments or supplements thereto, and at the time
of each of the Valero  Stockholders  Meeting and the UDS  Stockholders  Meeting,
contain any untrue  statement  of a material  fact or omit to state any material
fact required to be stated  therein or necessary in order to make the statements
therein,  in the light of the  circumstances  under  which  they are  made,  not
misleading.  The Joint Proxy Statement/Prospectus will comply, as of its mailing
date, as to form in all material  respects with all applicable  laws,  including
the  provisions  of the Exchange Act and the rules and  regulations  promulgated
thereunder,  except  that  no  representation  is made by UDS  with  respect  to
information supplied by Valero for inclusion therein.

(u) Labor  Relations;  Collective  Bargaining  Agreements.  Neither  UDS nor any
Subsidiary of UDS is a party to any  collective  bargaining or other labor union
contract  applicable to persons employed by UDS or any Subsidiary of UDS, and no
collective   bargaining  agreement  or  other  labor  union  contract  is  being
negotiated by UDS or any  Subsidiary of UDS. No labor  organization  or group of
employees  of UDS or any of its  Subsidiaries  has  made a  pending  demand  for
recognition or  certification,  and there are no representation or certification
proceedings or petitions seeking a representation  proceeding  presently pending
or threatened to be brought or filed, with the National Labor Relations Board or
any other labor relations tribunal or authority. To the knowledge of UDS, except
as would not  reasonably be expected to have a Material  Adverse  Effect on UDS,
(i) there is no labor dispute,  strike, slowdown or work stoppage against UDS or
any  Subsidiary of UDS pending or, to the knowledge of UDS,  threatened  against
UDS or any  Subsidiary of UDS and (ii) no unfair labor  practice or labor charge
or complaint has occurred with respect to UDS or any Subsidiary of UDS.

4.2 Representations  and Warranties of Valero.  Except as disclosed in a section
of the Valero disclosure  schedule  delivered to UDS concurrently  herewith (the
"Valero  Disclosure  Schedule")  corresponding to the subsection of this Section
4.2 to which such disclosure  applies,  Valero hereby represents and warrants to
UDS as follows:

(a) Corporate Organization.  (i) Valero is a corporation duly organized, validly
existing and in good  standing  under the laws of the State of Delaware.  Valero
has the corporate  power and authority to own or lease all of its properties and
assets and to carry on its  business as it is now being  conducted,  and is duly
licensed or qualified to do business in each jurisdiction in which the nature of
the business  conducted by it or the character or location of the properties and
assets owned or leased by it makes such  licensing or  qualification  necessary,
except  where the  failure to be so  licensed  or  qualified  would not,  either
individually or in the aggregate, have a Material Adverse Effect on Valero. True
and complete copies of the Restated  Certificate of Incorporation and By-Laws of
Valero, as in effect as of the date of this Agreement, have previously been made
available by Valero to UDS.

                           (ii) Each  Subsidiary of Valero (A) is duly organized
                  and validly  existing  under the laws of its  jurisdiction  of
                  organization, (B) is duly qualified to do business and in good
                  standing in all jurisdictions  (whether federal,  state, local
                  or foreign)  where its ownership or leasing of property or the
                  conduct of its business  requires it to be so qualified and in
                  which the  failure  to be so  qualified  would have a Material
                  Adverse  Effect on Valero and (C) has all requisite  corporate
                  power and authority to own or lease its  properties and assets
                  and to carry on its business as now conducted.

(b)  Capitalization.  (i) The authorized capital stock of Valero consists of (A)
150,000,000  shares of Valero  Common  Stock (each of which  includes one Valero
Right),  of which,  as of March 31,  2001,  61,016,165  shares  were  issued and
outstanding and 1,295,001 shares were held in treasury and (B) 20,000,000 shares
of preferred stock, par value $0.01 per share, of Valero (the "Valero  Preferred
Stock," together with the Valero Common Stock,  the "Valero Capital Stock"),  of
which no shares are issued and outstanding. From January 31, 2001 to the date of
this  Agreement,  no shares of Valero  Capital  Stock  have been  issued  except
pursuant to employee and director stock plans of Valero in effect as of the date
hereof (the "Valero Stock Plans").  All of the issued and outstanding  shares of
Valero Common Stock have been duly  authorized  and validly issued and are fully
paid,  nonassessable and free of preemptive  rights,  with no personal liability
attaching to the ownership  thereof.  As of the date of this  Agreement,  except
pursuant to the terms of options and stock issued pursuant to Valero Stock Plans
and pursuant to the Valero Rights,  Valero does not have and is not bound by any
outstanding  subscriptions,  options, warrants, calls, commitments or agreements
of any  character  calling for the  purchase or issuance of any shares of Valero
Capital  Stock or any  other  equity  securities  of  Valero  or any  securities
representing  the right to  purchase or  otherwise  receive any shares of Valero
Capital  Stock.  As of March 31, 2001,  no shares of Valero  Capital  Stock were
reserved for  issuance,  except for shares of Valero  Common Stock  reserved for
issuance upon the exercise of stock  options  pursuant to the Valero Stock Plans
and in respect of the employee and director  savings,  compensation and deferred
compensation  plans  described in the Valero 2000 10-K and  1,500,000  shares of
Junior  Participating  Preferred  Stock,  Series I,  reserved  for  issuance  in
connection with the Valero Rights Agreement. Valero has no Voting Debt issued or
outstanding.  Except for immaterial  amounts of directors'  qualifying shares in
foreign Subsidiaries of Valero, Valero owns, directly or indirectly,  all of the
issued  and  outstanding  shares  of  capital  stock or other  equity  ownership
interests of each Subsidiary of Valero,  free and clear of any Liens, and all of
such shares or equity ownership interests are duly authorized and validly issued
and are  fully  paid,  nonassessable  and  free of  preemptive  rights,  with no
personal liability  attaching to the ownership thereof.  No Subsidiary of Valero
has or is bound by any  outstanding  subscriptions,  options,  warrants,  calls,
commitments or agreements of any character  calling for the purchase or issuance
of any shares of capital stock or any other equity  security of such  Subsidiary
or any securities  representing  the right to purchase or otherwise  receive any
shares of capital stock or any other equity security of such Subsidiary.

(c) Authority;  No Violation.  (i) Valero has full corporate power and authority
to execute  and  deliver  this  Agreement  and to  consummate  the  transactions
contemplated  hereby.  The  execution  and  delivery of this  Agreement  and the
consummation of the transactions  contemplated hereby have been duly and validly
approved by the Board of Directors  of Valero.  The Board of Directors of Valero
has  directed  that this  Agreement  be  submitted  to Valero  stockholders  for
approval at a meeting of Valero  stockholders  for the purpose of approving  the
Merger and this Agreement (the "Valero Stockholders  Meeting"),  and, except for
the approval of the Merger and this  Agreement by majority  vote at a meeting of
Valero's  stockholders  at which a quorum is present  (the  "Valero  Stockholder
Approval"),  no other corporate  proceedings on the part of Valero are necessary
to approve  this  Agreement  and to  consummate  the  transactions  contemplated
hereby.  This  Agreement  has been duly and validly  executed  and  delivered by
Valero  and  (assuming  due  authorization,   execution  and  delivery  by  UDS)
constitutes a valid and binding obligation of Valero, enforceable against Valero
in accordance with its terms.

                           (ii)  Neither  the  execution  and  delivery  of this
                  Agreement  by Valero,  nor the  consummation  by Valero of the
                  transactions  contemplated  hereby,  nor  compliance by Valero
                  with any of the terms or provisions  hereof,  will (A) violate
                  any provision of the Restated  Certificate of Incorporation or
                  By-Laws  of  Valero  or (B)  assuming  that the  consents  and
                  approvals referred to in Section 4.2(d) are duly obtained, (x)
                  violate  any  statute,  code,  ordinance,   rule,  regulation,
                  judgment,  order,  writ,  decree or  injunction  applicable to
                  Valero,  any of its Subsidiaries or Non-Subsidiary  Affiliates
                  or any of its  properties  or assets or (y) violate,  conflict
                  with,  result in a breach of any  provision  of or the loss of
                  any benefit  under,  constitute  a default (or an event which,
                  with  notice or lapse of time,  or both,  would  constitute  a
                  default)  under,  result in the  termination  of or a right of
                  termination or cancellation under,  accelerate the performance
                  required by,  accelerate any right or benefit  provided by, or
                  result in the creation of any Lien upon any of the  properties
                  or assets of Valero, any of its Subsidiaries or Non-Subsidiary
                  Affiliates under any of the terms, conditions or provisions of
                  any note, bond, mortgage,  indenture,  deed of trust, license,
                  lease,  agreement or other  instrument  or obligation to which
                  Valero,  any of its Subsidiaries or Non-Subsidiary  Affiliates
                  is a party,  or by which  they or any of their  properties  or
                  assets may be bound or affected, except (in the case of clause
                  (y)  above)  for  such  violations,   conflicts,  breaches  or
                  defaults which, either individually or in the aggregate,  will
                  not have a Material Adverse Effect on Valero.

(d)  Consents and  Approvals.  Except for (i) the filing of a  notification  and
report form under the HSR Act and the  termination  or expiration of the waiting
period under the HSR Act,  (ii) the Other  Approvals,  (iii) the filing with the
SEC of the Joint Proxy Statement/Prospectus and the Form S-4, (iv) the filing of
the Certificate of Merger, (v) any consents, authorizations,  approvals, filings
or exemptions in connection  with  compliance  with the rules of the NYSE,  (vi)
such  filings and  approvals  as are  required to be made or obtained  under the
securities or "Blue Sky" laws of various states in connection  with the issuance
of the shares of Valero Common Stock  pursuant to this  Agreement and (vii) such
other consents,  approvals,  filings and  registrations  the failure of which to
obtain or make would not  reasonably  be  expected  to have a  Material  Adverse
Effect on Valero,  no consents or approvals of or filings or registrations  with
any  Governmental  Entity are necessary in connection with (A) the execution and
delivery by Valero of this Agreement and (B) the  consummation  by Valero of the
transactions contemplated by this Agreement.

(e)  Financial  Reports  and SEC  Documents.  The Valero 2000 10-K and all other
reports,  registration  statements,  definitive  proxy statements or information
statements filed or to be filed by Valero or any of its Subsidiaries  subsequent
to December 31, 1998 under the Securities Act or under Sections 13(a), 13(c), 14
and 15(d) of the Exchange Act, in the form filed, or to be filed  (collectively,
the "Valero  SEC  Documents"),  with the SEC (i)  complied or will comply in all
material  respects  as to  form  with  the  applicable  requirements  under  the
Securities  Act or the  Exchange  Act,  as the case  may be,  and (ii) as of its
filing date, did not or will not contain any untrue statement of a material fact
or omit to state a material fact  required to be stated  therein or necessary to
make the statements made therein, in light of the circumstances under which they
were made,  not  misleading;  and each of the  balance  sheets  contained  in or
incorporated  by  reference  into any such Valero SEC  Document  (including  the
related notes and schedules  thereto) fairly presents or will fairly present the
financial position of the entity or entities to which it relates as of its date,
and each of the  statements  of income and changes in  stockholders'  equity and
cash flows or equivalent  statements in such Valero SEC Documents (including any
related notes and schedules  thereto) fairly presents or will fairly present the
results of  operations,  changes  in  stockholders'  equity and  changes in cash
flows, as the case may be, of the entity or entities to which it relates for the
periods to which it relates,  in each case in accordance with GAAP  consistently
applied  during the  periods  involved,  except,  in each case,  as may be noted
therein,  subject to normal year-end audit  adjustments in the case of unaudited
statements.

(f)  Absence of  Undisclosed  Liabilities.  Except as  disclosed  in the audited
financial  statements  (or notes  thereto)  included  in the  Valero  2000 10-K,
neither  Valero nor any of its  Subsidiaries  had at December 31,  2000,  or has
incurred since that date through the date hereof, any liabilities or obligations
(whether absolute,  accrued,  contingent or otherwise) of any nature, except (a)
liabilities,  obligations  or  contingencies  which (i) are  accrued or reserved
against in the financial  statements in the Valero 2000 10-K or reflected in the
notes  thereto or (ii) were  incurred in the  ordinary  course of  business  and
consistent with past practices,  (b)  liabilities,  obligations or contingencies
which (i) would not  reasonably  be  expected  to have,  individually  or in the
aggregate,  a Material Adverse Effect on Valero, or (ii) have been discharged or
paid in full prior to the date  hereof,  and (c)  liabilities,  obligations  and
contingencies  which  are  of a  nature  not  required  to be  reflected  in the
consolidated  financial  statements of Valero and its  Subsidiaries  prepared in
accordance with GAAP consistently applied.

(g) Absence of Certain Changes or Events. (i) Since December 31, 2000, except as
set forth in Valero SEC Documents filed since December 31, 2000 and prior to the
date hereof,  no event or events have occurred that has had or would  reasonably
be expected to have, either individually or in the aggregate, a Material Adverse
Effect on Valero.

                           (ii)  Since   December  31,  2000,   Valero  and  its
                  Subsidiaries  have carried on their  respective  businesses in
                  all material respects in the ordinary course.

                           (iii)  Since  December  31,  2000,   Valero  has  not
                  declared any  dividends on Valero  Common Stock other than its
                  regular quarterly dividends.

(h) Legal  Proceedings.  There is no suit, action or proceeding or investigation
pending or, to the knowledge of Valero, threatened,  against or affecting Valero
or  any  of its  Subsidiaries  that  would,  individually  or in the  aggregate,
reasonably be expected to have a Material Adverse Effect on Valero, nor is there
any judgment,  decree,  injunction,  rule or order of any Governmental Entity or
arbitrator outstanding against Valero or its Subsidiaries having, or which would
reasonably  be  expected to have,  individually  or in the  aggregate,  any such
effect.

(i) Compliance with Applicable Law. Valero and each of its Subsidiaries hold all
licenses,  franchises,  permits  and  authorizations  necessary  for the  lawful
conduct of their  respective  businesses  under and  pursuant to each,  and have
complied in all respects with and are not in default under any,  applicable law,
statute, order, rule or regulation of any Governmental Entity relating to Valero
or any of its  Subsidiaries,  except  where the  failure  to hold such  license,
franchise,  permit or authorization or such  noncompliance or default would not,
either  individually  or in the  aggregate,  reasonably  be  expected  to have a
Material Adverse Effect on Valero.

(j) Contracts.  (i) Neither Valero nor any of its  Subsidiaries is a party to or
bound by any contract, arrangement, commitment or understanding (whether written
or oral)  (A)  which,  upon the  consummation  or  stockholder  approval  of the
transactions  contemplated  by this  Agreement,  will (either  alone or upon the
occurrence of any additional  acts or events) result in any payment  (whether of
severance  pay or  otherwise)  becoming  due from  UDS,  Valero,  the  Surviving
Corporation or any of their  respective  Subsidiaries to any director officer or
employee thereof, (B) which is a "material contract" (as such term is defined in
Item  601(b)(10) of Regulation S-K of the SEC) to be performed after the date of
this  Agreement  that has not been filed or  incorporated  by  reference  in the
Valero SEC  Documents  filed prior to the date hereof,  or (C) which  materially
restricts the conduct of any line of business by Valero or upon  consummation of
the  Merger  will  materially  restrict  the  ability  of UDS  or the  Surviving
Corporation  to  engage in any line of  business.  Each  contract,  arrangement,
commitment  or  understanding  of the type  described  in this  Section  4.2(j),
whether or not set forth in the Valero Disclosure Schedule or in such Valero SEC
Documents, is referred to herein as a "Valero Contract".

                           (ii) (A) Each Valero Contract is valid and binding on
                  Valero and any of its Subsidiaries that is a party thereto, as
                  applicable,  and in full force and effect, (B) Valero and each
                  of its Subsidiaries has in all material respects performed all
                  obligations  required to be performed by it to date under each
                  Valero  Contract,  except  where  such  noncompliance,  either
                  individually  or in the  aggregate,  would not  reasonably  be
                  expected to have a Material Adverse Effect on Valero,  and (C)
                  neither  Valero nor any of its  Subsidiaries  knows of, or has
                  received  notice of, the  existence  of any event or condition
                  which constitutes,  or, after notice or lapse of time or both,
                  will  constitute,  a material default on the part of Valero or
                  any of its Subsidiaries under any such Valero Contract, except
                  where such default,  either  individually or in the aggregate,
                  would not  reasonably  be expected to have a Material  Adverse
                  Effect on Valero.

(k) Environmental  Liability.  There are no legal,  administrative,  arbitral or
other proceedings,  claims,  actions,  causes of action,  private  environmental
investigations or remediation  activities or governmental  investigations of any
nature seeking to impose,  or that could reasonably result in the imposition of,
on Valero,  any  liability or  obligation  arising under common law or under any
local, state or federal environmental statute, regulation or ordinance including
CERCLA,  pending or threatened in writing  against  Valero,  which  liability or
obligation,  either  individually  or in  the  aggregate,  would  reasonably  be
expected to have a Material  Adverse Effect on Valero.  Valero is not subject to
any  agreement,  order,  judgment,  decree,  letter or memorandum by or with any
court,  governmental  authority,  regulatory  agency or third party imposing any
liability or obligation with respect to the foregoing that, either  individually
or in the  aggregate,  would  reasonably be expected to have a Material  Adverse
Effect on Valero.

(l) Employee Benefit Plans; Labor Matters.  (i) The Internal Revenue Service has
issued a favorable determination letter with respect to each Valero Plan that is
intended to be a "qualified  plan"  within the meaning of Section  401(a) of the
Code ("Valero  Qualified  Plans") and the related trust, and such  determination
letter has not been revoked.  No circumstances exist and no events have occurred
that could adversely affect the qualified status of any Valero Qualified Plan or
the related  trust  which  could not be  corrected  under the  Internal  Revenue
Service's  Employee  Plans  Compliance   Resolution  System  (Revenue  Procedure
2001-17)  without  material  liability to Valero.  No Valero Plan is intended to
meet the requirements of Code Section 501(c)(9).(i)

         (ii)     With respect  to  each Valero Plan that is subject  to Titl IV
                  or Section 302 of ERISA or Section 412 or 4971 of the Code:(A)
                  there does not exist any accumulated funding deficiency within
                  the  meaning of  Section  412  of  the  Code or Section 302 of
                  ERISA, whether or not waived; (B) the fair market value of the
                  assets  of  such  Valero  Plan equals or exceeds the actuarial
                  present  value  of all accrued benefits under such Valero Plan
                  (whether or not vested) on an accumulated  benefit  obligation
                  basis,  based  on  the  most  recent actuarial report for such
                  plan; (C)  no  reportable  event within the meaning of Section
                  4043(c)  of ERISA  for which the 30-day notice requirement has
                  not  been  waived  has  occurred,  and the consummation of the
                  transactions contemplated by this Agreement will not result in
                  the occurrence of any  such reportable event; (D) all premiums
                  to  the  PBGC  have been timely paid in full; (E) no liability
                  (other than for  premiums to the PBGC) under Title IV of ERISA
                  has been or is expected to be incurred by Valero or any of its
                  Subsidiaries;  and (F) the PBGC has not instituted proceedings
                  to terminate any such Valero Plan and, to Valero's  knowledge,
                  no condition exists that presents a risk that such proceedings
                  will  be  instituted  or  which would constitute grounds under
                  Section  4042 of ERISA for the termination of, or the appoint-
                  ment of a trustee to administer, any such Valero Plan.

        (iii)     Except as would not reasonably be expected, individually or in
                  the  aggregate,  to  have a Material Adverse Effect on Valero,
                  (A)  each   of   the   Valero  Plans  has  been  operated  and
                  administered  in  all  material  respects  in  accordance with
                  applicable law and administrative rules and regulations of any
                  Governmental Entity, including, but not limited to, ERISA  and
                  the  Code,  and  (B) there are no pending or threatened claims
                  (other than  claims  for  benefits  in  the  ordinary course),
                  lawsuits   or   arbitrations  which   have  been  asserted  or
                  instituted against  the  Valero Benefit Plans, any fiduciaries
                  thereof  with  respect  to  their duties to the Valero Benefit
                  Plans  or  the  assets  of  any of the trusts under any of the
                  Valero  Benefit  Plans  which  could reasonably be expected to
                  result  in  any  material  liability  of  Valero or any of its
                  Subsidiaries to the PBGC, the U.S. Department of the Treasury,
                  the  U.S.  Department  of  Labor, any Valero Benefit Plan, any
                  participant in a Valero Benefit Plan, or any other party.

         (iv)     No  Valero  Benefit Plan is a Multiemployer Plan or a Multiple
                  Employer Plan.

(m) Intellectual Property.  Except as would not reasonably be expected to have a
Material Adverse Effect on Valero,  (i) Valero and its Subsidiaries  own, or are
licensed to use, all Intellectual Property used in and necessary for the conduct
of their business as it is currently conducted, (ii) to the knowledge of Valero,
the use of  Intellectual  Property  by  Valero  and its  Subsidiaries  does  not
infringe  on or  otherwise  violate the rights of any third  party,  and, to the
extent such Intellectual  Property is licensed,  its use is in accordance in all
material respects with the applicable  license pursuant to which Valero acquired
the right to use such Intellectual  Property,  (iii) to the knowledge of Valero,
no third party is challenging, infringing on or otherwise violating any right of
Valero  in  the  Intellectual  Property,  (iv)  neither  Valero  nor  any of its
Subsidiaries  has received  any written  notice of any pending  claim,  order or
proceeding with respect to any  Intellectual  Property used in and necessary for
the  conduct of  Valero's  and its  Subsidiaries'  business  as it is  currently
conducted, and (v) to the knowledge of Valero, no Intellectual Property is being
used or enforced by Valero or its Subsidiaries in a manner that would reasonably
be expected to result in the abandonment,  cancellation or  unenforceability  of
any Intellectual  Property used in and necessary for the conduct of Valero's and
its Subsidiaries' business as it is currently conducted.
(n) State Takeover  Laws;  Rights Plan. (i) The Board of Directors of Valero has
approved this Agreement and the  transactions  contemplated by this Agreement as
required under Section 203 of the DGCL and any other  applicable  state takeover
laws so that any such state  takeover  laws will not apply to this  Agreement or
any of the transactions contemplated hereby.

                           (ii) Valero has taken all action,  if any,  necessary
                  or  appropriate  so that the entering into of this  Agreement,
                  and the consummation of the transactions  contemplated hereby,
                  do not and will not  result in the  ability  of any  person to
                  exercise any Valero Rights under the Valero  Rights  Agreement
                  or enable or require the Valero  Rights to  separate  from the
                  shares of Valero Common Stock to which they are attached or to
                  be triggered or become exercisable.  No "Distribution Date" or
                  "Shares  Acquisition  Date" (as such terms are  defined in the
                  Valero Rights Agreement) has occurred.

(o) Opinion of  Financial Advisor. Valero  has  received  the  opinion of Credit
Suisse First Boston Corporation and  Morgan  Stanley & Co. Incorporated, in each
case  dated the date hereof, to the effect that the Merger Consideration is fair
to Valero from a financial point of view.

(p) Board Approval.  The Board of Directors of Valero,  at a meeting duly called
and held, has by unanimous vote of those  directors  present (i) determined that
this Agreement and the transactions  contemplated hereby are advisable,  fair to
and in the best  interests  of the  stockholders  of Valero,  (ii)  approved and
adopted this Agreement,  and (iii) recommended that the plan of merger contained
in this Agreement be adopted by the holders of Valero Common Stock.

(q) Broker's  Fees.  Neither Valero nor any of its  Subsidiaries  nor any of its
respective  officers or directors  has employed any broker or finder or incurred
any liability for any broker's fees,  commissions or finder's fees in connection
with the transactions contemplated by this Agreement,  excluding fees to be paid
to Morgan Stanley & Co. Incorporated and Credit Suisse First Boston Corporation.

(r) Taxes.  (i) Except as would not reasonably be expected,  individually  or in
the aggregate,  to have a Material Adverse Effect on Valero,  (A) each of Valero
and its  Subsidiaries  has duly and timely filed all Tax Returns  required to be
filed by it, and all such Tax Returns  are true,  complete  and  accurate in all
respects; (B) Valero and each of its Subsidiaries has paid all Taxes required to
be paid by it,  and has paid all Taxes that it was  required  to  withhold  from
amounts owing to any employee, creditor or third party; (C) there are no pending
or, to the knowledge of Valero, threatened audits, examinations, investigations,
deficiencies, claims or other proceedings in respect of Taxes relating to Valero
or any Subsidiary of Valero; (D) there are no liens for Taxes upon the assets of
Valero or any  Subsidiary of Valero,  other than liens for current Taxes not yet
due and liens for Taxes that are being  contested  in good faith by  appropriate
proceedings;  (E) neither Valero nor any of its  Subsidiaries  has requested any
extension of time within which to file any Tax Returns in respect of any taxable
year  which  have  not  subsequently  been  filed  when  due  (pursuant  to such
extension), nor provided or been requested to provide any waivers of the time to
assess any Taxes that are pending or outstanding;  (F) the consolidated  federal
income Tax Returns of Valero have been  examined,  or the statute of limitations
has closed,  with respect to all taxable years  through and  including  July 31,
1997; (G) neither Valero nor any of its Subsidiaries has any liability for Taxes
of any Person (other than Valero and its Subsidiaries) under Treasury Regulation
Section 1.1502-6 (or any comparable  provision of state,  local or foreign law);
and (H) neither  Valero nor any Subsidiary of Valero is a party to any agreement
(with any Person other than Valero and/or any of its  Subsidiaries)  relating to
the allocation or sharing of Taxes which is currently in force.

                           (ii)   Valero   has   not   constituted    either   a
                  "distributing   corporation"  or  a  "controlled  corporation"
                  within the  meaning of Section  355(a)(1)(A)  of the Code in a
                  distribution of stock intended to qualify under Section 355(a)
                  of the  Code  (i) in the two  years  prior to the date of this
                  Agreement (or will  constitute  such a corporation  in the two
                  years  prior to the  Closing  Date) or (ii) in a  distribution
                  which  otherwise  constitutes  part of a "plan" or  "series of
                  related  transactions" within the meaning of Section 355(e) of
                  the Code in conjunction with the Merger.

(s)  Reorganization  under the Code. As of the date of this  Agreement,  neither
Valero  nor any of its  Subsidiaries  has taken any  action or knows of any fact
that  is  reasonably   likely  to  prevent  the  Merger  from  qualifying  as  a
"reorganization" within the meaning of Section 368(a) of the Code.

(t) Form S-4; Joint Proxy  Statement/Prospectus.  None of the  information to be
supplied  by  Valero  or its  Subsidiaries  in the Form S-4 or the  Joint  Proxy
Statement/Prospectus  will,  at the  time  of the  mailing  of the  Joint  Proxy
Statement/Prospectus  and any amendments or supplements thereto, and at the time
of each of the Valero  Stockholders  Meeting and the UDS  Stockholders  Meeting,
contain any untrue  statement  of a material  fact or omit to state any material
fact required to be stated  therein or necessary in order to make the statements
therein,  in the light of the  circumstances  under  which  they are  made,  not
misleading.  The Joint Proxy Statement/Prospectus will comply, as of its mailing
date, as to form in all material  respects with all applicable  laws,  including
the  provisions  of the Exchange Act and the rules and  regulations  promulgated
thereunder,  except that no  representation  is made by Valero  with  respect to
information supplied by UDS for inclusion therein.

(u) Neither  Valero nor any  Subsidiary  of Valero is a party to any  collective
bargaining  or other  labor union  contract  applicable  to persons  employed by
Valero or any Subsidiary of Valero,  and no collective  bargaining  agreement or
other labor union  contract is being  negotiated by Valero or any  Subsidiary of
Valero.  No labor  organization  or group of  employees  of Valero or any of its
Subsidiaries  has made a pending demand for  recognition or  certification,  and
there are no representation or certification  proceedings or petitions seeking a
representation  proceeding  presently  pending  or  threatened  to be brought or
filed,  with the National  Labor  Relations  Board or any other labor  relations
tribunal  or  authority.  To the  knowledge  of  Valero,  except  as  would  not
reasonably be expected to have a Material Adverse Effect on Valero, (i) there is
no labor  dispute,  strike,  slowdown  or work  stoppage  against  Valero or any
Subsidiary of Valero pending or, to the knowledge of Valero,  threatened against
Valero or any  Subsidiary  of Valero and (ii) no unfair labor  practice or labor
charge or complaint  has occurred  with respect to Valero or any  Subsidiary  of
Valero.

(v) Financing.  Valero  will have available on the Closing Date sufficient funds
to enable it to consummate the transactions contemplated by this Agreement.

                                   ARTICLE V
                    COVENANTS RELATING TO CONDUCT OF BUSINESS

5.1  Covenants  of UDS.  During the period from the date of this  Agreement  and
continuing   until  the  Effective  Time,  UDS  agrees  as  to  itself  and  its
Subsidiaries  that (unless Valero shall otherwise agree in writing and except as
expressly  contemplated  or  permitted by this  Agreement  or a  correspondingly
numbered subsection of the UDS Disclosure Schedule):

(a)  Ordinary  Course.  (i)  UDS and  its  Subsidiaries  shall  carry  on  their
respective  businesses in the ordinary course  consistent with past practices in
all material respects, in substantially the same manner as heretofore conducted,
and shall use its reasonable best efforts  consistent with the other  provisions
of this  Agreement to keep  available the services of their  respective  present
officers and key  employees,  preserve  intact their  present lines of business,
maintain  their rights and  franchises  and preserve  their  relationships  with
customers,  suppliers and others having  business  dealings with them to the end
that their ongoing  businesses  shall not be impaired in any material respect at
the Effective Time.

                           (ii) UDS shall  not,  and shall not permit any of its
                  Subsidiaries  to,  (A)  enter  into any new  material  line of
                  business or (B) without the prior  written  consent of Valero,
                  which will not be  unreasonably  withheld,  incur or commit to
                  any capital  expenditures or any obligations or liabilities in
                  connection  therewith,  other than  capital  expenditures  and
                  obligations  or  liabilities  in connection  therewith (I) not
                  exceeding  $25 million  individually,  or $100  million in the
                  aggregate,  or (II)  contemplated  by the 2001 capital  budget
                  approved  by  the  UDS  Board  of  Directors  and   previously
                  disclosed to Valero.

(b) Dividends; Changes in Share Capital. UDS shall not, and shall not permit any
of its  Subsidiaries  to,  and shall not  propose  to,  (i)  declare  or pay any
dividends on or make other distributions in respect of any of its capital stock,
except (x) the declaration  and payment of regular  quarterly cash dividends not
in excess of $0.125 per share of UDS Common  Stock with usual record and payment
dates for such  dividends in  accordance  with past dividend  practice,  (y) the
payment of accrued  amounts  on any UDS Toprs  pursuant  to the terms of, and in
connection  with the redemption of, such UDS Toprs as required by their terms as
in effect as of the date hereof and (z) the  declaration  and payment of regular
dividends  from a wholly  owned  Subsidiary  of UDS to UDS or to another  wholly
owned Subsidiary of UDS in accordance with past dividend  practice,  (ii) split,
combine or reclassify  any of its capital stock or issue or authorize or propose
the  issuance  of  any  other  securities  in  respect  of,  in  lieu  of  or in
substitution  for, shares of its capital stock,  except for any such transaction
by a wholly owned  Subsidiary  of UDS which  remains a wholly  owned  Subsidiary
after consummation of such transaction, or (iii) repurchase, redeem or otherwise
acquire any shares of its capital stock or any  securities  convertible  into or
exercisable for any shares of its capital stock.

(c)  Issuance  of  Securities.  UDS shall  not,  and shall not permit any of its
Subsidiaries  to, issue,  deliver,  sell,  pledge or dispose of, or authorize or
propose the issuance,  delivery,  sale,  pledge or disposition of, any shares of
its capital stock of any class,  any Voting Debt or any  securities  convertible
into or exercisable for, or any rights,  warrants,  calls or options to acquire,
any such  shares or Voting  Debt,  or enter  into any  commitment,  arrangement,
undertaking or agreement  with respect to any of the  foregoing,  other than (i)
the  issuance  of UDS Common  Stock (and the  associated  UDS  Rights)  upon the
exercise of UDS Stock  Options  outstanding  as of the date hereof in accordance
with their present terms, (ii) issuances,  sales or deliveries by a wholly-owned
Subsidiary  of UDS of  capital  stock to such  Subsidiary's  parent  or  another
wholly-owned  Subsidiary of UDS or (iii)  issuances in  accordance  with the UDS
Rights  Agreement.  UDS shall not contribute  any  additional  shares of capital
stock to any trust associated with the GSOP.

(d)  Governing  Documents.  Except to the  extent  required  to comply  with its
obligations hereunder or with applicable law, UDS shall not and shall cause each
of its  Subsidiaries  not to amend or  propose  to so amend its  certificate  of
incorporation or by-laws or similar organizational documents.

(e) No Acquisitions.  Except for acquisitions in the ordinary course of business
consistent  with past  practice that do not exceed $25 million  individually  or
$100  million in the  aggregate,  without the prior  written  consent of Valero,
which will not be unreasonably withheld, UDS shall not, and shall not permit any
of its Subsidiaries to, acquire or agree to acquire by merger or  consolidation,
or by purchasing a substantial  equity  interest in or a substantial  portion of
the  assets  of,  or by any  other  manner,  any  business  or any  corporation,
partnership,  association or other business  organization or division thereof or
otherwise  acquire or agree to acquire any assets  (excluding the acquisition of
assets used in the operations of the business of UDS and its Subsidiaries in the
ordinary course, which assets do not constitute a business unit, division or all
or substantially all of the assets of the transferor and which  acquisitions are
in the ordinary course of business consistent with past practice).

(f) No Dispositions. UDS shall not, and shall not permit any of its Subsidiaries
to, sell,  lease or otherwise  dispose of, or agree to sell,  lease or otherwise
dispose of, any of its assets  (including  capital stock of Subsidiaries of UDS)
other than in the ordinary course of business consistent with past practice.

(g)  Investments;  Indebtedness.  UDS shall not, and shall not permit any of its
Subsidiaries to, (i) make any loans,  advances or capital  contributions  to, or
investments in, any other Person,  other than (x) loans or investments by UDS or
a wholly owned  Subsidiary of UDS to or in UDS or any wholly owned Subsidiary of
UDS, (y) in the ordinary course of business  consistent with past practice which
are not, individually or in the aggregate,  material to UDS and its Subsidiaries
taken as a whole  (provided that none of such  transactions  referred to in this
clause (y)  presents a material  risk of making it more  difficult to obtain any
approval  or  authorization   required  in  connection  with  the  Merger  under
Regulatory  Law) or (ii)  except in the  ordinary  course  consistent  with past
practice under UDS's existing  authorized  commercial  paper program,  incur any
indebtedness  for borrowed money or guarantee any such  indebtedness  of another
Person, issue or sell any debt securities or warrants or other rights to acquire
any  debt  securities  of UDS or any of its  Subsidiaries,  guarantee  any  debt
securities of another  person,  enter into any "keep well" or other agreement to
maintain any  financial  statement  condition of another  Person (other than any
wholly  owned  Subsidiary)  or enter into any  arrangement  having the  economic
effect of any of the foregoing (collectively, "UDS Indebtedness").

(h) Tax-Free  Qualification.  UDS shall use its reasonable  best efforts not to,
and shall use its reasonable best efforts not to permit any of its  Subsidiaries
to, take any action  (including any action  otherwise  permitted by this Section
5.1) that would  reasonably be expected to prevent the Merger from qualifying as
a "reorganization" within the meaning of Section 368(a) of the Code.

(i)  Compensation.  Except  (x)  as  required  by law  or by  the  terms  of any
collective  bargaining  agreement or other agreement currently in effect between
UDS or any  Subsidiary of UDS and any director,  officer or employee  thereof or
(y) in the ordinary course of business consistent with past practice,  UDS shall
not (A) increase the amount of  compensation  of, or pay any  severance  to, any
director or employee of UDS or any material  Subsidiary  or business unit of UDS
(and UDS shall  consult  with Valero  before  effecting  or  proposing  any such
increase  with  respect  to  any  director,  officer  or  key  employee  of  the
foregoing),  or (B) make any increase in or  commitment to increase any employee
benefits,  grant any additional  UDS Stock  Options,  adopt or amend or make any
commitment  to  adopt  or  amend  any UDS  Benefit  Plan  or  fund  or make  any
contribution  to any UDS  Benefit  Plan or any  related  trust or other  funding
vehicles  (provided that, in any event,  any such increase,  commitment,  grant,
adoption,  amendment,  funding or  contribution  contemplated by this clause (B)
shall only be made after prior  consultation with Valero),  other than regularly
scheduled  contributions to trusts funding qualified plans. No UDS Stock Options
that are  issued  after the date  hereof and prior to the  Effective  Time shall
include  "reload"  features  or "change  in  control"  provisions  that would be
triggered by the transactions contemplated by this Agreement.

(j) Accounting Methods; Tax Elections.  Except as disclosed in UDS SEC Documents
filed prior to the date of this  Agreement,  or as  required  by a  Governmental
Entity,  UDS shall not change in any material  respect its methods of accounting
in effect at  December  30,  2000,  except as  required  by  changes  in GAAP as
concurred in by UDS's independent public  accountants.  UDS shall not (i) change
its fiscal year or any method of tax  accounting,  (ii) make any Tax election or
(iii) settle or compromise any liability for Taxes,  except in each case for any
such actions that,  individually  or in the  aggregate,  would not reasonably be
expected to have a Material Adverse Effect on UDS or as required by law.

(k) Certain Actions.  UDS and its Subsidiaries shall not take any action or omit
to take any action that would  reasonably  be expected to prevent or  materially
delay or  impede  the  consummation  of the  Merger  or the  other  transactions
contemplated  by this  Agreement or,  except in the ordinary  course of business
consistent with past practice, terminate, amend or modify any material provision
of, or waive any material rights under, any UDS Contract.

(l) No  Related  Actions.  UDS  shall  not,  and  shall  not  permit  any of its
Subsidiaries to, agree or commit to do any of the foregoing.

5.2 Covenants of Valero.  During the period from the date of this  Agreement and
continuing  until  the  Effective  Time,  Valero  agrees  as to  itself  and its
Subsidiaries  that  (unless UDS shall  otherwise  agree in writing and except as
expressly  contemplated  or  permitted by this  Agreement  or a  correspondingly
numbered subsection of the Valero Disclosure Schedule):

(a) Ordinary Course. Valero and its Subsidiaries shall carry on their respective
businesses in the ordinary course consistent with past practices in all material
respects,  in substantially the same manner as heretofore  conducted,  and shall
use their  reasonable  best efforts to preserve  intact their  present  lines of
business,  maintain their rights and franchises and preserve their relationships
with customers,  suppliers and others having business  dealings with them to the
end that their ongoing  businesses shall not be impaired in any material respect
at the Effective Time.

(b) Dividends;  Changes in Share Capital. Valero shall not, and shall not permit
any of its  Subsidiaries  to, and shall not  propose  to, (i) declare or pay any
dividends on or make other distributions in respect of any of its capital stock,
except (x) the declaration and payment of regular  quarterly cash dividends with
usual  record and  payment  dates for such  dividends  in  accordance  with past
dividend  practice and (y) the declaration and payment of regular dividends from
a  Subsidiary  of  Valero  to  Valero  or to  another  Subsidiary  of  Valero in
accordance with past dividend practice or (ii) split,  combine or reclassify any
of its capital  stock or issue or authorize or propose the issuance of any other
securities  in  respect  of, in lieu of or in  substitution  for,  shares of its
capital stock,  except for any such  transaction by a wholly owned Subsidiary of
Valero  which  remains a wholly  owned  Subsidiary  after  consummation  of such
transaction.

(c) Governing Documents.  Except (i) to the extent required to comply with their
respective  obligations hereunder or with applicable law or (ii) to increase the
number  of  shares  of  capital   stock   authorized  by  its   certificate   of
incorporation,  Valero shall not amend or propose to so amend its certificate of
incorporation or by-laws.

(d) Tax-Free Qualification. Valero shall use its reasonable best efforts not to,
and shall use its reasonable best efforts not to permit any of its  Subsidiaries
to, take any action  (including any action  otherwise  permitted by this Section
5.2) that would  reasonably be expected to prevent the Merger from qualifying as
a "reorganization" within the meaning of Section 368(a) of the Code.

(e) Certain Actions.  Valero and its  Subsidiaries  shall not take any action or
omit to take any  action  that  would  reasonably  be  expected  to  prevent  or
materially  delay  or  impede  the  consummation  of the  Merger  or  the  other
transactions contemplated by this Agreement.

(f) No  Related  Actions.  Valero  shall  not,  and  shall not permit any of its
Subsidiaries to, agree or commit to do any of the foregoing.

5.3 Governmental  Filings. UDS and Valero shall (A) confer on a reasonable basis
with each other and (B) report to each other (to the extent  permitted by law or
regulation or any applicable  confidentiality agreement) on operational matters.
UDS and Valero shall file all reports  required to be filed by each of them with
the SEC (and all other Governmental Entities) between the date of this Agreement
and the Effective  Time and shall,  if requested by the other and (to the extent
permitted by law or  regulation  or any  applicable  confidentiality  agreement)
deliver  to the  other  party  copies  of all such  reports,  announcements  and
publications promptly upon request.

5.4 Control of Other Party's Business. Nothing contained in this Agreement shall
give UDS,  directly  or  indirectly,  the right to  control  or direct  Valero's
operations  or give  Valero,  directly  or  indirectly,  the right to control or
direct UDS's  operations  prior to the  Effective  Time.  Prior to the Effective
Time,  each of UDS and  Valero  shall  exercise,  consistent  with the terms and
conditions  of  this  Agreement,  complete  control  and  supervision  over  its
respective operations.

                                   ARTICLE VI
                              ADDITIONAL AGREEMENTS

6.1 Preparation of Proxy Statement;  Stockholders  Meetings.  (a) As promptly as
reasonably practicable following the date hereof, Valero and UDS shall cooperate
in preparing  and each shall cause to be filed with the SEC mutually  acceptable
proxy materials which shall constitute the Joint Proxy  Statement/Prospectus and
Valero  shall  prepare  and file  with the SEC the Form  S-4.  The  Joint  Proxy
Statement/Prospectus  will be included as a prospectus in and will  constitute a
part of the Form S-4 as  Valero's  prospectus.  Each of Valero and UDS shall use
reasonable best efforts to have the Joint Proxy Statement/Prospectus  cleared by
the SEC and the Form S-4 declared  effective by the SEC and to keep the Form S-4
effective as long as is necessary to consummate the Merger and the  transactions
contemplated  hereby.  Valero and UDS shall,  as promptly as  practicable  after
receipt  thereof,  provide each other with copies of any written  comments,  and
advise  each  other  of any oral  comments,  with  respect  to the  Joint  Proxy
Statement/Prospectus  or Form  S-4  received  from the SEC.  The  parties  shall
cooperate  and provide the other party with a reasonable  opportunity  to review
and   comment   on   any   amendment   or   supplement   to  the   Joint   Proxy
Statement/Prospectus and the Form S-4 prior to filing such with the SEC and will
provide  each  other  with a  copy  of all  such  filings  made  with  the  SEC.
Notwithstanding  any other  provision  herein to the  contrary,  no amendment or
supplement  (including  by  incorporation  by  reference)  to  the  Joint  Proxy
Statement/Prospectus  or the Form S-4 shall be made without the approval of both
Valero and UDS, which approval  shall not be  unreasonably  withheld or delayed;
provided that, with respect to documents filed by a party which are incorporated
by reference in the Form S-4 or Joint Proxy Statement/Prospectus,  this right of
approval  shall  apply only with  respect to  information  relating to the other
party or its business, financial condition or results of operations. Valero will
use reasonable best efforts to cause the Joint Proxy  Statement/Prospectus to be
mailed to Valero stockholders, and UDS will use reasonable best efforts to cause
the Joint Proxy  Statement/Prospectus to be mailed to UDS stockholders,  in each
case, as promptly as practicable after the Form S-4 is declared  effective under
the  Securities  Act. Each party will advise the other party,  promptly after it
receives notice thereof, of the time when the Form S-4 has become effective, the
issuance of any stop order,  the suspension of the  qualification  of the Valero
Common Stock issuable in connection  with the Merger for offering or sale in any
jurisdiction,  or any  request  by the  SEC for  amendment  of the  Joint  Proxy
Statement/Prospectus  or the Form S-4.  If, at any time  prior to the  Effective
Time,  any  information  relating to Valero or UDS,  or any of their  respective
affiliates,  officers  or  directors,  is  discovered  by Valero or UDS and such
information should be set forth in an amendment or supplement to any of the Form
S-4 or the Joint Proxy  Statement/Prospectus so that any of such documents would
not include any  misstatement  of a material  fact or omit to state any material
fact necessary to make the  statements  therein,  in light of the  circumstances
under  which  they  were  made,  not  misleading,  the  party  discovering  such
information  shall  promptly  notify the other  party  hereto and, to the extent
required by law, rules or  regulations,  an appropriate  amendment or supplement
describing  such   information   shall  be  promptly  filed  with  the  SEC  and
disseminated to the stockholders of Valero and UDS.

                  (b) UDS shall duly take all lawful action to call, give notice
of,  convene and hold the UDS  Stockholders  Meeting as soon as practicable on a
date  determined in accordance  with the mutual  agreement of Valero and UDS for
the purpose of obtaining the UDS  Stockholder  Approval and,  subject to Section
6.5, shall take all lawful action to solicit the UDS Stockholder  Approval.  The
Board of Directors of UDS shall, subject to the proper exercise of its fiduciary
duties, recommend the adoption of the plan of merger contained in this Agreement
by the  stockholders  of UDS to the effect as set forth in Section  4.1(p)  (the
"UDS Recommendation"), and shall not, unless Valero makes a Change in the Valero
Recommendation,  (x) withdraw, modify or qualify (or propose to withdraw, modify
or qualify) in any manner adverse to Valero the UDS  Recommendation  or (y) take
any action or make any statement in connection with the UDS Stockholders Meeting
inconsistent  with  such  recommendation  (collectively,  a  "Change  in the UDS
Recommendation"); provided, however, that the Board of Directors of UDS may make
a Change in the UDS Recommendation pursuant to Section 6.5 hereof.

                  (c) Valero  shall duly take all  lawful  action to call,  give
notice  of,  convene  and  hold  the  Valero  Stockholders  Meeting  as  soon as
practicable  on a date  determined  in accordance  with the mutual  agreement of
Valero and UDS for the purpose of obtaining the Valero Stockholder  Approval and
shall take all lawful  action to solicit the Valero  Stockholder  Approval.  The
Board of  Directors  of Valero  shall,  subject  to the proper  exercise  of its
fiduciary duties, recommend the adoption of the plan of merger contained in this
Agreement  by the  stockholders  of Valero to the  effect  set forth in  Section
4.2(p) and the approval of the issuance of Valero  Common Stock in the Merger by
the stockholders of Valero (the "Valero Recommendation"),  and shall not, unless
UDS makes a Change in the UDS  Recommendation,  (x) withdraw,  modify or qualify
(or propose to  withdraw,  modify or  qualify) in any manner  adverse to UDS the
Valero Recommendation or (y) take any action or make any statement in connection
with the  Valero  Stockholders  Meeting  inconsistent  with such  recommendation
(collectively, a "Change in the Valero Recommendation").

6.2 Valero Board of  Directors.  At the  Effective  Time,  Valero shall take all
requisite  action to (i) if  necessary to give effect to the  succeeding  clause
(ii), expand its Board of Directors by up to four members and (ii) cause four of
the  current  members  of the UDS  Board of  Directors,  as  shall  be  mutually
determined  by UDS  and  Valero,  to be  appointed  to its  Board  of  Directors
(collectively,  the  "UDS  Board  Designees").  At  the  annual  meeting  of the
stockholders of Valero  immediately  following the Effective  Time,  Valero will
take all action  necessary to nominate and recommend each UDS Board Designee for
reelection  to the  Valero  Board  of  Directors,  with at least  one UDS  Board
Designee  serving  in each  class of  directors  and no more  than two UDS Board
Designees serving in the same class of directors.

6.3 Access to Information.  Upon reasonable notice,  each party shall (and shall
cause its  Subsidiaries  to)  afford to the  officers,  employees,  accountants,
counsel,  financial  advisors  and  other  representatives  of the  other  party
reasonable  access during normal business hours,  during the period prior to the
Effective Time, to all its properties, books, contracts,  commitments,  records,
officers and  employees  and,  during such  period,  such party shall (and shall
cause its  Subsidiaries  to)  furnish  promptly to the other party (a) a copy of
each  report,  schedule,   registration  statement  and  other  document  filed,
published,  announced  or  received  by it during  such  period  pursuant to the
requirements  of Federal or state  securities laws or the HSR Act, as applicable
(other  than  documents  which such party is not  permitted  to  disclose  under
applicable law), and (b) all other  information  concerning it and its business,
properties and personnel as such other party may reasonably  request;  provided,
however,  that either party may restrict the foregoing access to the extent that
(i) any law, treaty, rule or regulation of any Governmental Entity applicable to
such party or any contract  requires such party or its  Subsidiaries to restrict
or prohibit access to any such properties or information or (ii) the information
is subject to  confidentiality  obligations  to a third party.  The parties will
hold any  information  obtained  pursuant to this Section 6.3 in  confidence  in
accordance  with,  and shall  otherwise  be subject  to, the  provisions  of the
confidentiality  agreement  dated  April 23,  2001,  between UDS and Valero (the
"Confidentiality Agreement"),  which Confidentiality Agreement shall continue in
full  force and  effect.  Any  investigation  by either  Valero or UDS shall not
affect the representations and warranties of the other.

6.4  Reasonable  Best Efforts.  (a) Subject to the terms and  conditions of this
Agreement,  each party hereto will use its  reasonable  best efforts to take, or
cause to be  taken,  all  actions,  and do,  or cause  to be  done,  all  things
necessary,  proper or advisable  under this  Agreement and  applicable  laws and
regulations to consummate the Merger and the other transactions  contemplated by
this  Agreement  as soon as  practicable  after the date hereof,  including  (i)
preparing and filing as promptly as practicable all  documentation to effect all
necessary applications,  notices, petitions, filings, and other documents and to
obtain as promptly as practicable all Necessary Consents and all other consents,
waivers,  licenses,   orders,   registrations,   approvals,   permits,  rulings,
authorizations  and  clearances  necessary or advisable to be obtained  from any
third party and/or any Governmental  Entity in order to consummate the Merger or
any of the other transactions contemplated by this Agreement (collectively,  the
"Required  Approvals")  and (ii) using its reasonable best efforts to obtain all
such Necessary  Consents and the Required  Approvals.  In furtherance and not in
limitation of the foregoing, each of Valero and UDS agrees (i) to make (A) prior
to May 31,  2001,  an  appropriate  filing of a  Notification  and  Report  Form
pursuant to the HSR Act with respect to the  transactions  contemplated  hereby,
(B)  as  promptly  as  practicable,   appropriate   filings  with  the  European
Commission,  if required,  in accordance  with  applicable  competition,  merger
control,  antitrust,  investment  or  similar  laws,  and  (C)  as  promptly  as
practicable,  all other  necessary  filings  with  other  Governmental  Entities
relating to the Merger, and, to supply as promptly as practicable any additional
information or documentation  that may be requested  pursuant to such laws or by
such  authorities  and to use reasonable best efforts to cause the expiration or
termination of the applicable  waiting periods under the HSR Act and the receipt
of Required  Approvals under such other laws or from such authorities as soon as
practicable and (ii) not to extend any waiting period under the HSR Act or enter
into any agreement  with the FTC or the DOJ not to consummate  the  transactions
contemplated  by this  Agreement,  except with the prior written  consent of the
other parties hereto (which shall not be unreasonably withheld or delayed).

                  (b)  Each of UDS and  Valero  shall,  in  connection  with the
efforts referenced in Section 6.4(a) to obtain all Required  Approvals,  use its
reasonable  best efforts to (i)  cooperate  in all  respects  with each other in
connection   with  any  filing  or  submission   and  in  connection   with  any
investigation or other inquiry,  including any proceeding initiated by a private
party,  (ii)  subject to  applicable  law,  permit the other  party to review in
advance  any  proposed  written  communication  between it and any  Governmental
Entity,  (iii)  promptly  inform  each  other  of  (and,  at the  other  party's
reasonable  request,  supply to such other  party) any  communication  (or other
correspondence or memoranda) received by such party from, or given by such party
to,  the DOJ,  the FTC or any  other  Governmental  Entity  and of any  material
communication  received or given in connection  with any proceeding by a private
party, in each case regarding any of the transactions  contemplated  hereby, and
(iv) consult with each other in advance to the extent practicable of any meeting
or  conference  with the DOJ,  the FTC or any other  Governmental  Entity or, in
connection with any proceeding by a private party, with any other Person, and to
the extent permitted by the DOJ, the FTC or such other  applicable  Governmental
Entity or other  Person,  give the other  party the  opportunity  to attend  and
participate in such meetings and conferences.

                  (c) In  furtherance  and not in limitation of the covenants of
the parties  contained in Section 6.4(a) and 6.4(b),  if any  administrative  or
judicial  action or proceeding,  including any proceeding by a private party, is
instituted  (or  threatened  to  be  instituted)   challenging  any  transaction
contemplated  by this  Agreement as violative of any  regulatory  law, or if any
statute, rule, regulation, executive order, decree, injunction or administrative
order is enacted,  entered,  promulgated  or enforced by a  Governmental  Entity
which  would  make the  Merger or the  other  transactions  contemplated  hereby
illegal  or  would  otherwise   prohibit  or  materially  impair  or  delay  the
consummation of the Merger or the other  transactions  contemplated  hereby, UDS
shall  cooperate  with Valero in all respects in  responding  thereto,  and each
shall  use  its  respective  reasonable  best  efforts  in  responding  thereto,
including (i) contesting and resisting any such action or proceeding and to have
vacated,  lifted,  reversed or overturned  any decree,  judgment,  injunction or
other order, whether temporary,  preliminary or permanent, that is in effect and
that  prohibits,  prevents or restricts  consummation of the Merger or the other
transactions  contemplated  by this  Agreement and to have such  statute,  rule,
regulation,   executive  order,  decree,   injunction  or  administrative  order
repealed,  rescinded or made  inapplicable  so as to permit  consummation of the
transactions  contemplated  by this  Agreement  and  (ii)  holding  separate  or
otherwise  disposing of or conducting their business in a specified  manner,  or
agreeing  to sell,  hold  separate  or  otherwise  dispose of or  conduct  their
business in a specified manner or permitting the sale, holding separate or other
disposition of, assets of Valero,  UDS or their  respective  Subsidiaries or the
conducting  of  their  business  in  a  specified  manner.  Notwithstanding  the
foregoing or any other provision of this Agreement,  nothing in this Section 6.4
shall limit a party's  right to  terminate  this  Agreement  pursuant to Section
8.1(b)  or  8.1(c)  so long as such  party  has up to  then  complied  with  its
obligations under this Section 6.4.

                  (d) Each of  Valero  and UDS and  their  respective  Boards of
Directors  shall, if any state takeover  statute or similar statute  (including,
without  limitation,  Section  203 of  the  DGCL)  becomes  applicable  to  this
Agreement,  the Merger or any other transactions  contemplated  hereby, take all
action reasonably necessary to ensure that the Merger and the other transactions
contemplated  by this Agreement may be consummated as promptly as practicable on
the terms  contemplated  hereby and  otherwise  to  minimize  the effect of such
statute or regulation on this Agreement,  the Merger and the other  transactions
contemplated hereby.

6.5  Acquisition  Proposals.  (a)  UDS  agrees  that  neither  it nor any of its
Subsidiaries  nor any of the officers and  directors of UDS or its  Subsidiaries
shall,  and that it shall use its  reasonable  best efforts to cause its and its
Subsidiaries'  employees,  agents and representatives  (including any investment
banker,  attorney or accountant  retained by it or any of its  Subsidiaries) not
to,  directly or  indirectly,  (i)  initiate,  solicit,  encourage  or knowingly
facilitate any inquiries or the making of any proposal or offer with respect to,
or  a  transaction  to  effect,  a  merger,   reorganization,   share  exchange,
consolidation, business combination, recapitalization,  liquidation, dissolution
or similar transaction involving UDS or any of its Significant Subsidiaries,  or
any purchase or sale of 20% or more of the consolidated  assets (including stock
of its  Subsidiaries)  of it and its  Subsidiaries,  taken  as a  whole,  or any
purchase  or sale of, or tender or  exchange  offer for,  its equity  securities
that, if  consummated,  would result in any Person (or the  stockholders of such
Person)  beneficially  owning  securities  representing 20% or more of its total
voting power (or of the  surviving  parent  entity in such  transaction)  or the
voting power of any of its Significant Subsidiaries (any such proposal, offer or
transaction  (other  than a proposal  or offer  made by any other  party to this
Agreement  or  an  Affiliate  thereof)  being  hereinafter  referred  to  as  an
"Acquisition   Proposal"),   (ii)  have  any  discussion  with  or  provide  any
confidential  information  or  data to any  Person  relating  to an  Acquisition
Proposal,  or engage in any negotiations  concerning an Acquisition Proposal, or
knowingly  facilitate  any effort or attempt to make or implement an Acquisition
Proposal,  (iii)  approve  or  recommend,  or  propose  publicly  to  approve or
recommend,  any Acquisition Proposal or (iv) approve or recommend, or propose to
approve or recommend, or execute or enter into, any letter of intent,  agreement
in principle, merger agreement, acquisition agreement, option agreement or other
similar  agreement  or  propose  publicly  or agree  to do any of the  foregoing
related to any Acquisition Proposal.

(b)  Notwithstanding  anything in this  Agreement to the contrary,  UDS (and its
Board of  Directors)  shall be  permitted to (A) comply with Rule 14d-9 and Rule
14e-2 promulgated under the Exchange Act with regard to an Acquisition  Proposal
(to the extent applicable),  (B) effect a Change in the UDS  Recommendation,  or
(C) engage in discussions or  negotiations  with, or provide any information to,
any Person in response to an unsolicited bona fide written Acquisition  Proposal
by any such Person, if and only to the extent that, in any such case referred to
in clause (B) or (C), (I) the UDS  Stockholders  Meeting shall not have occurred
other than as a result of a breach by UDS of its obligations pursuant to Section
6.1,  (II) (x) in the case of clause (B) above,  it has received an  unsolicited
bona  fide  written  Acquisition  Proposal  from a third  party and its Board of
Directors concludes in good faith that such Acquisition  Proposal  constitutes a
Superior  Proposal  and (y) in the  case of  clause  (C)  above,  its  Board  of
Directors  concludes  in good faith that there is a reasonable  likelihood  that
such  Acquisition  Proposal could constitute a Superior  Proposal,  (III) in the
case of clause (B) or (C) above,  its Board of  Directors,  after receipt of the
advice of UDS's  outside  counsel,  determines  in good  faith  that  there is a
reasonable   probability   that  the  failure  to  take  such  action  would  be
inconsistent  with its  fiduciary  duties under  applicable  law,  (IV) prior to
providing  any  information  or  data  to  any  Person  in  connection  with  an
Acquisition  Proposal by any such Person,  its Board of Directors  receives from
such Person an executed  confidentiality  agreement  having  provisions that are
customary  in such  agreements,  as advised by  counsel,  provided  that if such
confidentiality agreement contains provisions that are less restrictive than the
comparable  provision,  or  omits  restrictive  provisions,   contained  in  the
Confidentiality  Agreement, then the Confidentiality Agreement will be deemed to
be amended  to contain  only such less  restrictive  provisions  or to omit such
restrictive  provisions,  as the case may be,  and (V)  prior to  providing  any
information or data to any Person or entering into  discussions or  negotiations
with any Person,  it notifies Valero  promptly of such  inquiries,  proposals or
offers received by, any such information requested from, or any such discussions
or  negotiations   sought  to  be  initiated  or  continued  with,  any  of  its
representatives  indicating,  in connection  with such notice,  the name of such
Person and the material  terms and  conditions  of any  inquiries,  proposals or
offers. UDS agrees that it will promptly keep Valero reasonably  informed of the
status and terms of any inquiries,  proposals or offers and the status and terms
of any discussions or  negotiations,  including the identity of the party making
such  inquiry,  proposal or offer.  UDS agrees that it will,  and will cause its
officers,  directors and  representatives  to, immediately cease and cause to be
terminated any activities,  discussions or negotiations  existing as of the date
of this Agreement  with any parties  (other than the parties to this  Agreement)
conducted heretofore with respect to any Acquisition  Proposal.  UDS agrees that
it will use reasonable best efforts to promptly inform its directors,  officers,
key employees,  agents and representatives of the obligations undertaken in this
Section 6.5.  Nothing in this Section 6.5 shall (x) permit UDS to terminate this
Agreement (except as specifically provided in Article VIII hereof) or (y) affect
or limit any other obligation of Valero or UDS under this Agreement.

6.6 Fees and  Expenses.  Subject  to Section  8.2,  whether or not the Merger is
consummated,  all Expenses  incurred in connection  with this  Agreement and the
transactions  contemplated  hereby  shall be paid by the  party  incurring  such
Expenses,  except Expenses incurred in connection with the filing,  printing and
mailing of the Joint  Proxy  Statement/Prospectus  and Form S-4,  which shall be
shared equally by Valero and UDS.

6.7  Directors'  and  Officers'  Indemnification  and  Insurance.  Following the
Effective  Time,  Valero  shall (i)  indemnify  and hold  harmless,  and provide
advancement  of  expenses  to,  all past and  present  directors,  officers  and
employees of UDS and its  Subsidiaries  (in all of their  capacities) (A) to the
same extent such persons are  indemnified  or have the right to  advancement  of
expenses as of the date of this  Agreement by UDS pursuant to UDS's  Certificate
of Incorporation,  By-laws and indemnification  agreements, if any, in existence
on the date hereof  with,  or for the benefit of, any  directors,  officers  and
employees of UDS and its Subsidiaries and (B) without  limitation to clause (A),
to the  fullest  extent  permitted  by law,  in each case for acts or  omissions
occurring at or prior to the  Effective  Time  (including  for acts or omissions
occurring in connection with the approval of this Agreement and the consummation
of  the  transactions  contemplated  hereby),  (ii)  include  and  cause  to  be
maintained  in effect in the  Surviving  Corporation's  (or any successor to the
business of the Surviving Corporation)  certificate of incorporation and by-laws
for a period  of six  years  after  the  Effective  Time,  provisions  regarding
elimination of liability of directors,  indemnification  of officers,  directors
and employees and  advancement of expenses which are, in the aggregate,  no less
advantageous to the intended  beneficiaries  than the  corresponding  provisions
contained in the current  Certificate  of  Incorporation  and By-laws of UDS and
(iii) cause to be maintained by the Surviving  Corporation  (or any successor to
the business of the Surviving  Corporation)  for a period of six years after the
Effective  Time the  current  policies of  directors'  and  officers'  liability
insurance and fiduciary  liability  insurance  maintained by UDS (provided  that
Valero (or any such  successor) may substitute  therefor one or more policies of
at least the same coverage and amounts  containing  terms and  conditions  which
are, in the  aggregate,  no less  advantageous  to the insured)  with respect to
claims  arising  from facts or events that  occurred on or before the  Effective
Time; provided,  however,  that in no event shall Valero (or any such successor)
be  required to expend in any one year an amount in excess of 200% of the annual
premiums currently paid by UDS for such insurance; and, provided further that if
the annual premiums of such insurance  coverage  exceed such amount,  Valero (or
any such successor) shall obtain a policy with the greatest  coverage  available
for a cost not exceeding  such amount.  The  obligations  of Valero (or any such
successor)  under this Section 6.7 shall not be terminated or modified in such a
manner as to adversely  affect any  indemnitee  to whom this Section 6.7 applies
without the consent of such affected  indemnitee (it being expressly agreed that
the indemnitees to whom this Section 6.7 applies and their  respective heirs and
other  representatives  shall be third-party  beneficiaries  of, and entitled to
enforce, this Section 6.7).

6.8 Employee Benefits. (a) Following the Effective Time until the first to occur
of (i) the first  anniversary  of the Effective  Time and (ii) December 31, 2002
(such shorter  period  referred to herein as the "Benefit  Protection  Period"),
Valero shall  provide,  or shall cause to be provided,  to  individuals  who are
employees of UDS and its Subsidiaries  immediately before the Effective Time and
who continue to be employed by Valero and its  Subsidiaries  after the Effective
Time (the "UDS  Employees")  Benefit  Plans  (other  than any  equity-based  UDS
Benefit  Plans)  that are,  in the  aggregate,  not less  favorable  than  those
generally  provided to UDS Employees as of the date hereof,  as disclosed by UDS
to Valero immediately prior to the date of this Agreement.  After the expiration
of the Benefit Protection Period, Valero shall provide, or cause to be provided,
to UDS Employees  compensation and employee benefit plans and programs that are,
in the  aggregate,  not less favorable  than those  generally  provided to other
similarly situated employees of Valero and its Subsidiaries. After the Effective
Time, the equity-based benefits to be provided to an eligible UDS Employee shall
be pursuant to the equity-based benefit plans and programs provided to similarly
situated  employees of Valero.  Nothing  contained  herein shall be construed to
prevent the  termination of employment of any UDS Employee;  provided,  however,
that in the event of a qualifying  termination  of any UDS  Employee  during the
Benefit Protection  Period,  Valero shall provide,  or cause to be provided,  to
such  terminated  UDS  Employee  severance  benefits  that are not less than the
amount of severance benefits that would have been payable under the terms of the
UDS severance plan or policy listed on Section 6.8(a) of the Company  Disclosure
Letter as in effect as of the date  hereof  that is  applicable  to any such UDS
Employee.  Notwithstanding  anything  contained  herein  to  the  contrary,  UDS
Employees  who are covered  under a  collective  bargaining  agreement  shall be
provided the benefits that are required by such collective  bargaining agreement
from time to time.

(a) (b) For all  purposes  under the  employee  benefit  plans of Valero and its
Subsidiaries  providing  benefits to any UDS Employee  after the Effective  Time
(the "New Plans"),  each UDS Employee shall be credited with his or her years of
service  with UDS and its  Subsidiaries  and  predecessor  employers  before the
Effective Time, to the same extent as such UDS Employee was entitled, before the
Effective  Time, to credit for such service under any similar UDS Benefit Plans,
except to the extent such credit would result in a duplication  of benefits.  In
addition,  and without  limiting the generality of the  foregoing:  (i) each UDS
Employee shall be immediately eligible to participate, without any waiting time,
in any and all New Plans to the extent  coverage  under  such New Plan  replaces
coverage  under a UDS  Benefit  Plan in  which  such UDS  Employee  participated
immediately  before the  Effective  Time  (such  plans,  collectively,  the "Old
Plans");  (ii)  for  purposes  of  each  New  Plan  providing  medical,  dental,
pharmaceutical  and/or vision  benefits to any UDS Employee,  Valero shall cause
all pre-existing condition exclusions and actively-at-work  requirements of such
New Plan to be waived for such employee and his or her covered  dependents,  and
Valero shall cause any eligible  expenses  incurred by such  employee and his or
her  covered  dependents  during  the  portion  of the plan year of the Old Plan
ending on the date such employee's  participation in the  corresponding New Plan
begins to be taken into account  under such New Plan for purposes of  satisfying
all deductible, coinsurance and maximum out-of-pocket requirements applicable to
such employee and his or her covered  dependents for the applicable plan year as
if such amounts had been paid in  accordance  with such New Plan;  and (iii) for
purposes of each New Plan  providing  long-term or short-term  disability,  life
insurance or other welfare benefits (other than medical, dental,  pharmaceutical
and/or vision benefits) to any UDS Employee, Valero shall cause all pre-existing
condition  exclusions of such New Plan to be waived for such employee and his or
her covered dependents.

(c) Valero will honor,  in accordance  with their terms,  all vested and accrued
benefit  obligations to, and contractual rights of, current and former employees
of UDS and its Subsidiaries  which are disclosed on UDS's Disclosure  Schedules,
including,  without limitation,  the "change of control" provisions contained in
the UDS  Benefit  Plans  listed on the Section  6.8(c) of the Valero  Disclosure
Schedule.  Nothing in this Agreement  shall be interpreted as preventing  Valero
from amending,  modifying or terminating any UDS Benefit Plan or other contract,
arrangement,  commitment or  understanding,  in accordance  with their terms and
applicable law.(d)

6.9 Public  Announcements.  Valero and UDS shall use reasonable  best efforts to
develop a joint  communications  plan and each shall use reasonable best efforts
(i) to ensure that all press releases and other public  statements  with respect
to the  transactions  contemplated  hereby shall be  consistent  with such joint
communications  plan and (ii) unless otherwise  required by applicable law or by
obligations  pursuant to any listing  agreement  with or rules of any securities
exchange, to consult with each other before issuing any press release or, to the
extent  practical,  otherwise  making any public  statement with respect to this
Agreement or the transactions contemplated hereby. In addition to the foregoing,
except  to  the  extent   disclosed  in  or  consistent  with  the  Joint  Proxy
Statement/Prospectus  in  accordance  with the  provisions  of Section  6.1, and
subject to Section 6.5(b),  neither Valero nor UDS shall issue any press release
or otherwise make any public statement or disclosure  concerning the other party
or the other  party's  business,  financial  condition or results of  operations
without the consent of the other party,  which consent shall not be unreasonably
withheld or delayed.

6.10 Listing of Shares of Valero Common Stock.  Valero shall use its  reasonable
best  efforts  to cause the  shares of Valero  Common  Stock to be issued in the
Merger and the shares of Valero  Common Stock to be reserved  for issuance  upon
exercise  of the UDS Stock  Options  to be  approved  for  listing  on the NYSE,
subject to official notice of issuance, prior to the Closing Date.

6.11 Rights Agreements. (a)  The  Board  of  Directors  of Valero shall take all
action to the extent necessary (including amending  the Valero Rights Agreement)
in  order  to  render the Valero Rights inapplicable to the Merger and the other
transactions contemplated by this Agreement.

                  (b) The Board of Directors of UDS shall take all action to the
extent  necessary  (including  amending  the UDS Rights  Agreement)  in order to
render the UDS  Rights  inapplicable  to the  Merger and the other  transactions
contemplated  by  this  Agreement.  Except  in  connection  with  the  foregoing
sentence,  the Board of  Directors of UDS shall not,  without the prior  written
consent of Valero,  (i) amend or waive any provision of the UDS Rights Agreement
or (ii) take any action with respect to, or make any  determination  under,  the
UDS Rights Agreement,  including a redemption of the UDS Rights, in each case in
order to facilitate any Acquisition Proposal with respect to UDS.

6.12 Affiliates. Not less than 45 days prior to the date of the UDS Stockholders
Meeting,  UDS shall deliver to Valero a letter  identifying  all persons who, in
the judgment of UDS, may be deemed at the time this  Agreement is submitted  for
adoption by the  stockholders  of UDS,  "affiliates" of UDS for purposes of Rule
145 under the Securities Act and applicable SEC rules and regulations,  and such
list shall be updated as necessary to reflect changes from the date thereof. UDS
shall use reasonable  best efforts to cause each person  identified on such list
to deliver to Valero not later  than ten days  prior to the  Effective  Time,  a
written  agreement  substantially  in the form  attached as Exhibit A hereto (an
"Affiliate Agreement").

6.13 Section 16 Matters.  Prior to the Effective Time, Valero and UDS shall take
all such steps as may be required to cause any  dispositions of UDS Common Stock
(including   derivative   securities  with  respect  to  UDS  Common  Stock)  or
acquisitions  of Valero  Common  Stock  (including  derivative  securities  with
respect to Valero Common Stock) resulting from the transactions  contemplated by
Article II or Article III of this Agreement by each individual who is subject to
the reporting  requirements of Section 16(a) of the Exchange Act with respect to
UDS or will  become  subject  to such  reporting  requirements  with  respect to
Valero, to be exempt under Rule 16b-3 promulgated under the Exchange Act.

6.14 UDS Indebtedness.  With respect to UDS Indebtedness issued under indentures
qualified under the Trust Indenture Act of 1939, and any other UDS  Indebtedness
the terms of which require  Valero to assume such debt in order to avoid default
thereunder  (collectively,  the "Assumed Indentures"),  Valero shall execute and
deliver to the trustees or other representatives in accordance with the terms of
the respective Assumed Indentures, supplemental indentures or other instruments,
in form  satisfactory  to the  respective  trustees  or  other  representatives,
expressly  assuming the  obligations of UDS with respect to the due and punctual
payment of the principal of (and premium, if any) and interest,  if any, on, and
conversion  obligations  under,  all debt  securities  issued  by UDS  under the
Assumed  Indentures  and the  due and  punctual  performance  of all the  terms,
covenants and  conditions  of the Assumed  Indentures to be kept or performed by
UDS and shall deliver such  supplemental  indentures or other instruments to the
respective trustees or other representatives under the Assumed Indentures.

6.15 Accountants'  Letter. UDS shall use its reasonable best efforts to cause to
be  delivered  to  Valero  a  letter  from its  independent  public  accountants
addressed to Valero,  dated a date within two  Business  Days before the date on
which the Form S-4 shall  become  effective,  in form and  substance  reasonably
satisfactory  to  Valero  and  customary  in scope  and  substance  for  letters
delivered by  independent  public  accountants in connection  with  registration
statements similar to the Form S-4.

                                  ARTICLE VII
                              CONDITIONS PRECEDENT

7.1  Conditions  to Each Party's Obligation to Effect the Merger. The respective
obligations  of  UDS  and  Valero  to  effect  the  Merger  are  subject  to the
satisfaction  or  waiver  on  or  prior  to  the  Closing  Date of the following
conditions:

(a) Stockholder  Approval. (i) UDS  shall  have  obtained  the  UDS  Stockholder
Approval and (ii) Valero shall have obtained the Valero Stockholder Approval.

(b) No Injunctions or Restraints;  Illegality. No law shall have been adopted or
promulgated,  and no  temporary  restraining  order,  preliminary  or  permanent
injunction  or other  order  issued by a court or other  Governmental  Entity of
competent  jurisdiction  shall be in  effect,  having  the  effect of making the
Merger illegal or otherwise prohibiting consummation of the Merger.

(c) HSR Act; Other Approvals. (i) The waiting period (and any extension thereof)
applicable  to the Merger under the HSR Act shall have been  terminated or shall
have expired,  and (ii) all Other  Approvals  shall have been  obtained,  except
those Other Approvals the failure of which to obtain would not,  individually or
in the  aggregate,  reasonably be expected to have a Material  Adverse Effect on
Valero or UDS.

(d) NYSE  Listing.  The shares of Valero Common Stock to be issued in the Merger
and such other  shares of Valero  Common  Stock to be reserved  for  issuance in
connection  with the Merger  shall have been  approved  for listing on the NYSE,
subject to official notice of issuance.

(e)  Effectiveness  of the Form  S-4.  The Form S-4  shall  have  been  declared
effective by the SEC under the Securities  Act and no stop order  suspending the
effectiveness  of the  Form  S-4  shall  have  been  issued  by the  SEC  and no
proceedings for that purpose shall have been initiated or threatened by the SEC.

7.2 Additional Conditions to Obligations of Valero. The obligations of Valero to
effect the Merger are subject to  the  satisfaction,  or waiver by Valero, on or
prior to the Closing Date, of the following conditions:

(a) Representations  and Warranties.  Each of the representations and warranties
of UDS set  forth in this  Agreement  that is  qualified  as to  materiality  or
Material   Adverse   Effect  shall  be  true  and  correct,   and  each  of  the
representations and warranties of UDS set forth in this Agreement that is not so
qualified shall be true and correct in all material respects, in each case as of
the date of this  Agreement  and as of the Closing Date as though made on and as
of the  Closing  Date  (except  to the  extent  that  such  representations  and
warranties  speak as of another  date,  in which case such  representations  and
warranties  shall be so true  and  correct  as of such  other  date);  provided,
however,  that no such  representations  or  warranties  shall be deemed to have
failed to be true and correct for  purposes of this  Section  7.2(a)  unless the
failure  of  such  representations  and  warranties  to  be  true  and  correct,
disregarding  for this  purpose  all  qualifications  and  exceptions  contained
therein relating to materiality or Material Adverse Effect, would,  individually
or in the aggregate, reasonably be expected to have a Material Adverse Effect on
UDS; and Valero shall have received a certificate of an executive officer of UDS
to such effect.

(b)  Performance  of Obligations of UDS. UDS shall have performed or complied in
all material respects with all agreements and covenants required to be performed
by it under this  Agreement  at or prior to the Closing  Date;  and Valero shall
have received a certificate of an executive officer of UDS to such effect.

(c) Tax Opinion. Valero shall have received from Wachtell, Lipton, Rosen & Katz,
counsel to Valero,  a written  opinion dated the Closing Date to the effect that
for federal  income tax purposes the Merger will  constitute a  "reorganization"
within the meaning of Section  368(a) of the Code.  In rendering  such  opinion,
counsel to Valero  shall be  entitled  to rely upon  customary  assumptions  and
representations    reasonably   satisfactory   to   such   counsel,    including
representations set forth in certificates of officers of Valero and UDS.

7.3  Additional  Conditions to  Obligations  of UDS. The  obligations  of UDS to
effect the Merger are subject to the satisfaction, or waiver by UDS, on or prior
to the Closing Date, of the following additional conditions:

(a) Representations  and Warranties.  Each of the representations and warranties
of Valero set forth in this  Agreement  that is qualified as to  materiality  or
Material   Adverse   Effect  shall  be  true  and  correct,   and  each  of  the
representations and warranties of Valero set forth in this Agreement that is not
so qualified shall be true and correct in all material respects, in each case as
of the date of this  Agreement  and as of the Closing Date as though made on and
as of the  Closing  Date  (except to the extent  that such  representations  and
warranties  speak as of another  date,  in which case such  representations  and
warranties  shall be so true  and  correct  as of such  other  date);  provided,
however,  that no such  representations  or  warranties  shall be deemed to have
failed to be true and correct for  purposes of this  Section  7.3(a)  unless the
failure  of  such  representations  and  warranties  to  be  true  and  correct,
disregarding  for this  purpose  all  qualifications  and  exceptions  contained
therein relating to materiality or Material Adverse Effect, would,  individually
or in the aggregate, reasonably be expected to have a Material Adverse Effect on
Valero;  and UDS shall have  received a certificate  of an executive  officer of
Valero to such effect.

(b)  Performance  of  Obligations  of Valero.  Valero  shall have  performed  or
complied in all material respects with all agreements and covenants  required to
be performed by it under this Agreement at or prior to the Closing Date; and UDS
shall have  received a  certificate  of an  executive  officer of Valero to such
effect.

(c) Tax  Opinion.  UDS shall have  received  from  Jones,  Day,  Reavis & Pogue,
counsel to UDS, a written  opinion dated the Closing Date to the effect that for
federal income tax purposes the Merger will constitute a "reorganization" within
the meaning of Section 368(a) of the Code. In rendering such opinion, counsel to
UDS shall be entitled to rely upon  customary  assumptions  and  representations
reasonably satisfactory to such counsel,  including representations set forth in
certificates of officers of Valero and UDS.

                                  ARTICLE VIII
                            TERMINATION AND AMENDMENT

8.1  Termination.  This  Agreement  may be  terminated  at any time prior to the
Effective  Time,  by action taken or authorized by the Board of Directors of the
terminating party or parties, and except as specifically provided below, whether
before or after the Valero Stockholders Meeting or the UDS Stockholders Meeting:

(a)      By mutual written consent of Valero and UDS;

(b) By either Valero or UDS, if the Effective Time shall not have occurred on or
before May 3, 2002 (the "Termination Date");  provided,  however, that the right
to terminate this Agreement  under this Section 8.1(b) shall not be available to
any  party  whose  failure  to  fulfill  any  obligation  under  this  Agreement
(including  such  party's  obligations  set forth in  Section  6.4) has been the
primary cause of, or resulted in, the failure of the Effective  Time to occur on
or before the Termination Date;

(c) By either Valero or UDS, if any Governmental Entity (i) shall have issued an
order,  decree or ruling or taken any other action (which the parties shall have
used their reasonable best efforts to resist, resolve or lift, as applicable, in
accordance  with Section 6.4)  permanently  restraining,  enjoining or otherwise
prohibiting the  transactions  contemplated  by this Agreement,  and such order,
decree, ruling or other action shall have become final and nonappealable or (ii)
shall  have  failed  to issue an  order,  decree  or ruling or to take any other
action  which is  necessary  to fulfill  the  conditions  set forth in  Sections
7.1(c),  (d) or (e), as  applicable,  and such denial of a request to issue such
order, decree, ruling or the failure to take such other action shall have become
final and nonappealable (which order, decree, ruling or other action the parties
shall have used their  reasonable  best efforts to obtain,  in  accordance  with
Section 6.4);  provided,  however,  that the right to terminate  this  Agreement
under this Section  8.1(c) shall not be available to any party whose  failure to
comply with Section 6.4 has been the primary cause of such action or inaction;

(d) By either  Valero or UDS, if either the Valero  Stockholder  Approval or the
UDS  Stockholder  Approval  has not been  obtained  by reason of the  failure to
obtain  the  required  vote  at the  Valero  Stockholders  Meeting  or  the  UDS
Stockholders Meeting, as applicable;

(e) By  Valero,  if UDS shall  have  breached  or failed to  perform  any of its
representations,  warranties,  covenants or other  agreements  contained in this
Agreement,  such that the  conditions set forth in Section 7.2(a) or (b) are not
capable of being satisfied on or before the Termination Date;

(f) By UDS,  if Valero  shall  have  breached  or failed to  perform  any of its
representations,  warranties,  covenants or other  agreements  contained in this
Agreement,  such that the  conditions set forth in Section 7.3(a) or (b) are not
capable of being satisfied on or before the Termination Date;

(g) By UDS, if the Board of  Directors  of UDS has  provided  written  notice to
Valero that UDS intends to enter into a binding written agreement for a Superior
Proposal (with such termination becoming effective,  if Valero does not make the
offer  contemplated  by clause  (iii) below,  on the  business  day  immediately
following the five business day period contemplated thereby, or otherwise,  upon
UDS entering into such binding written agreement);  provided,  however, that (i)
UDS shall have complied with Section 6.5 hereof in all material  respects;  (ii)
UDS shall have (A)  notified  Valero in writing of its receipt of such  Superior
Proposal,  (B) further notified Valero in such writing that UDS intends to enter
into a binding  agreement  with  respect to such  Superior  Proposal  subject to
clause (iii) below and (C) attached  the most  current  written  version of such
Superior Proposal (or a summary  containing all material terms and conditions of
such Superior Proposal) to such notice;  (iii) Valero does not make, within five
business  days after  receipt of UDS's  written  notice  pursuant to clause (ii)
above,  an offer  that the  Board of  Directors  of UDS  shall  have  reasonably
concluded in good faith (following  consultation  with its financial advisor and
outside  counsel) is as favorable to the  stockholders  of UDS as such  Superior
Proposal;  and (iv) UDS pays the UDS  Termination Fee in accordance with Section
8.2(d) concurrently with such termination;

(h) By UDS, if Valero shall have (i) failed to make the Valero Recommendation or
effected a Change in the Valero  Recommendation  (or  resolved  to take any such
action),  whether  or not  permitted  by the terms  hereof,  or (ii)  materially
breached its obligations under this Agreement by reason of a failure to call the
Valero  Stockholders  Meeting in accordance  with Section 6.1(c) or a failure to
prepare and mail to its  stockholders  the Joint Proxy  Statement/Prospectus  in
accordance with Section 6.1(a); or

(i) By Valero,  if UDS shall have (i) failed to make the UDS  Recommendation  or
effected  a  Change  in the UDS  Recommendation  (or  resolved  to take any such
action),  whether  or not  permitted  by the terms  hereof,  or (ii)  materially
breached its obligations under this Agreement by reason of a failure to call the
UDS  Stockholders  Meeting in  accordance  with  Section  6.1(b) or a failure to
prepare and mail to its  stockholders  the Joint Proxy  Statement/Prospectus  in
accordance with Section 6.1(a).

8.2 Effect of Termination.  (a) In the event of termination of this Agreement by
either UDS or Valero as provided in Section 8.1, this Agreement  shall forthwith
become void and there shall be no  liability  or  obligation  on the part of any
party to this Agreement or their  respective  officers or directors  except with
respect to Section 4.1(q),  Section 4.2(o),  the second sentence of Section 6.3,
Section 6.6,  this Section 8.2 and Article IX, which  provisions  shall  survive
such  termination;  provided  that,  notwithstanding  anything  to the  contrary
contained  in this  Agreement,  neither  Valero  nor UDS  shall be  relieved  or
released from any liabilities or damages arising out of its willful and material
breach of this Agreement.

                  (b) If (A)  (I)  (x)  either  UDS or  Valero  terminates  this
Agreement  pursuant  to  Section  8.1(d)  (provided  that  the  basis  for  such
termination is the failure to obtain the UDS  Stockholder  Approval) or pursuant
to Section 8.1(b) without the UDS  Stockholders  Meeting having  occurred or (y)
Valero  terminates this Agreement  pursuant to Section 8.1(e),  (II) at any time
after the date of this  Agreement  and before such  termination  an  Acquisition
Proposal  with  respect to UDS shall have been  publicly  announced or otherwise
communicated  to the senior  management,  Board of Directors or  stockholders of
UDS, or UDS shall have breached in any material  respect its  obligations  under
Section 6.5, and (III) within  twelve months of such  termination  UDS or any of
its  Subsidiaries  enters  into any  definitive  agreement  with  respect to, or
consummates,  or the  Board  of  Directors  of  UDS  or any of its  Subsidiaries
recommends  that its  respective  stockholders  approve,  adopt or  accept,  any
Acquisition  Proposal,  or (B) Valero shall terminate this Agreement pursuant to
Section 8.1(i), then UDS shall promptly, but in no event later than one Business
Day after the date of such termination (or, in the case of clause (A), if later,
the date UDS or its  Subsidiary  enters into such  agreement  with respect to or
consummates  such Acquisition  Proposal),  pay Valero an amount equal to the UDS
Termination Fee, by wire transfer of immediately available funds.

                  (c) If (A)  (I)  (x)  either  UDS or  Valero  terminates  this
Agreement  pursuant  to  Section  8.1(d)  (provided  that  the  basis  for  such
termination  is the  failure  to obtain  the  Valero  Stockholder  Approval)  or
pursuant  to Section  8.1(b)  without  the Valero  Stockholders  Meeting  having
occurred or (y) UDS terminates this Agreement  pursuant to Section 8.1(f),  (II)
at any time after the date of this Agreement and before such  termination  there
shall have been  publicly  announced  or  otherwise  communicated  to the senior
management,  Board of  Directors  or  stockholders  of Valero a proposal for the
acquisition  by a  third  party  of  50% or  more  of  the  consolidated  assets
(including stock of its Subsidiaries) of Valero and its Subsidiaries, taken as a
whole,  or of  50% or  more  of its  total  voting  power,  whether  by  merger,
reorganization,    share   exchange,   consolidation,    business   combination,
recapitalization,  liquidation,  dissolution,  tender offer or exchange offer or
similar transaction and (III) within twelve months of such termination Valero or
any of its Subsidiaries enters into any definitive agreement with respect to, or
consummates,  or the Board of  Directors  of  Valero or any of its  Subsidiaries
recommends  that  its  respective  stockholders  approve,  adopt  or  accept,  a
transaction  contemplated  by  clause  (II),  or (B) UDS  shall  terminate  this
Agreement  pursuant to Section  8.1(h),  then Valero shall  promptly,  but in no
event later than one Business Day after the date of such termination (or, in the
case of clause (A), if later, the date Valero or its Subsidiary enters into such
agreement with respect to or consummates the transaction  contemplated by clause
(II)),  pay UDS an amount equal to the Valero  Termination Fee, by wire transfer
of immediately available funds.

                  (d) If UDS  terminates  this  Agreement  pursuant  to  Section
8.1(g),  UDS shall pay Valero in an amount equal to the UDS Termination  Fee, by
wire  transfer  of  immediately   available   funds,   concurrently   with  such
termination.

                  (e)  The  parties  hereto   acknowledge  that  the  agreements
contained  in  this  Section  8.2  are an  integral  part  of  the  transactions
contemplated  by this Agreement,  and that,  without these  agreements,  neither
party  would  enter into this  Agreement;  accordingly,  if either  party  fails
promptly to pay any amount due pursuant to this  Section  8.2,  and, in order to
obtain  such  payment,  the other  party  commences  a suit  which  results in a
judgment  against  such party for the fee set forth in this  Section  8.2,  such
party shall pay to the other party its costs and expenses (including  attorneys'
fees and expenses) in connection  with such suit,  together with interest on the
amount of the fee at the prime rate of Citibank, N.A. in effect on the date such
payment was required to be made,  notwithstanding the provisions of Section 6.6.
The  parties  hereto  agree that any remedy or amount  payable  pursuant to this
Section 8.2 shall not preclude any other remedy or amount payable hereunder, and
shall not be an exclusive  remedy,  for any willful and  material  breach of any
representation, warranty, covenant or agreement contained in this Agreement.

8.3 Amendment.  This Agreement may be amended by the parties  hereto,  by action
taken or authorized by their respective Boards of Directors,  at any time before
or after the Valero Stockholder Approval or the UDS Stockholder  Approval,  but,
after  any  such  approval,  no  amendment  shall  be  made  which  by law or in
accordance  with the  rules of any  relevant  stock  exchange  requires  further
approval by such stockholders without such further approval.  This Agreement may
not be amended  except by an instrument  in writing  signed on behalf of each of
the parties hereto.

8.4  Extension;  Waiver.  At any time prior to the Effective  Time,  the parties
hereto,  by action taken or authorized by their respective  Boards of Directors,
may, to the extent legally  allowed,  (i) extend the time for the performance of
any of the obligations or other acts of the other parties hereto, (ii) waive any
inaccuracies in the  representations  and warranties  contained herein or in any
document  delivered  pursuant hereto and (iii) waive  compliance with any of the
agreements or conditions  contained herein. Any agreement on the part of a party
hereto to any such  extension  or waiver  shall be valid  only if set forth in a
written  instrument  signed on behalf of such party. The failure of any party to
this  Agreement  to assert any of its rights  under this  Agreement or otherwise
shall not constitute a waiver of those rights.

                                   ARTICLE IX
                               GENERAL PROVISIONS

9.1  Non-Survival of  Representations,  Warranties and  Agreements.  None of the
representations, warranties, covenants and other agreements in this Agreement or
in any instrument  delivered  pursuant to this  Agreement,  including any rights
arising  out of any  breach  of  such  representations,  warranties,  covenants,
agreements and other  provisions,  shall survive the Effective Time,  except for
those covenants,  agreements and other provisions contained herein that by their
terms apply or are to be performed in whole or in part after the Effective  Time
and this Article IX.

9.2 Notices. All notices and other communications  hereunder shall be in writing
and  shall be  deemed  duly  given  (a) on the  date of  delivery  if  delivered
personally,  or by telecopy or facsimile,  upon verbal  confirmation of receipt,
(b) on the first  Business Day  following the date of dispatch if delivered by a
recognized  next-day courier service, or (c) on the fifth Business Day following
the date of mailing if delivered by registered or certified mail, return receipt
requested,  postage  prepaid.  All notices  hereunder  shall be delivered as set
forth below,  or pursuant to such other  instructions  as may be  designated  in
writing by the party to receive such notice:

(i)      if to Valero to:

                                    Valero Energy Corporation
                                    One Valero Place
                                    San Antonio, Texas 78212

                                    Attention: General Counsel

                                    with a copy to:

                                    Wachtell, Lipton, Rosen & Katz
                                    51 West 52nd Street
                                    New York, New York 10019

                                    Attention: Edward D. Herlihy, Esq.

(ii)     if to UDS to:

                                    Ultramar Diamond Shamrock Corporation
                                    6000 North Loop
                                    1604 West
                                    San Antonio, Texas 78249-1112

                                    Attn: Chief Administrative & Legal Officer

                                    with a copy to:

                                    Jones, Day, Reavis & Pogue
                                    North Point
                                    901 Lakeside Avenue
                                    Cleveland, Ohio 44114-1190

                                    Attention: Lyle Ganske, Esq.

9.3  Interpretation.  When a reference  is made in this  Agreement  to Articles,
Sections,  Exhibits  or  Schedules,  such  reference  shall be to an  Article or
Section of or Exhibit or Schedule to this Agreement unless otherwise  indicated.
The table of contents and headings contained in this Agreement are for reference
purposes only and shall not affect in any way the meaning or  interpretation  of
this Agreement. Whenever the words "include," "includes" or "including" are used
in this  Agreement,  they shall be deemed to be followed  by the words  "without
limitation."  In addition,  each  Section of this  Agreement is qualified by the
matters  set  forth  with  respect  to such  Section  on the  Valero  Disclosure
Schedule, the UDS Disclosure Schedule and the other Schedules to this Agreement,
and such other  Sections of this Agreement to the extent that the matter in such
Section of such  Schedule is  disclosed  in such a way as to make its  relevance
called for by such other Section of this Agreement readily apparent.

9.4  Counterparts.  This Agreement may be executed in one or more  counterparts,
all of which shall be  considered  one and the same  agreement  and shall become
effective when one or more  counterparts have been signed by each of the parties
and delivered to the other party, it being understood that both parties need not
sign the same counterpart.

9.5 Entire  Agreement;  No Third Party  Beneficiaries.  (a) This Agreement,  the
Confidentiality  Agreement and the exhibits and  schedules  hereto and the other
agreements  and  instruments  of the parties  delivered in  connection  herewith
constitute  the  entire   agreement  and  supersede  all  prior  agreements  and
understandings,  both  written and oral,  among the parties  with respect to the
subject  matter  hereof,  except that,  for purposes of the  definition of "best
efforts" as used in Sections 6.4(a) and 6.4(c) and interpreting the right of UDS
to  terminate  this  Agreement  under  Section  8.1(f)  upon breach by Valero of
Sections 6.4(a) and 6.4(c),  the parties agree that it is proper to refer to the
course of their discussions prior to entering into this Agreement.

                  (b) This  Agreement  shall be binding upon and inure solely to
the  benefit of each party  hereto,  and nothing in this  Agreement,  express or
implied, is intended to or shall confer upon any other Person any right, benefit
or remedy of any nature  whatsoever under or by reason of this Agreement,  other
than Section 6.7 (which is intended to be for the benefit of the Persons covered
thereby).

9.6  Governing Law. This Agreement shall be governed and construed in accordance
with the laws of the State of  Delaware  (without giving effect to choice of law
principles thereof).

9.7  Severability.  If any term or other provision of this Agreement is invalid,
illegal or incapable of being  enforced by any law or public  policy,  all other
terms and provisions of this Agreement shall  nevertheless  remain in full force
and  effect  so long as the  economic  or legal  substance  of the  transactions
contemplated  hereby is not  affected  in any manner  materially  adverse to any
party.  Upon such  determination  that any term or other  provision  is invalid,
illegal or incapable of being  enforced,  the parties hereto shall  negotiate in
good faith to modify this  Agreement so as to effect the original  intent of the
parties  as  closely  as  possible  in an  acceptable  manner in order  that the
transactions  contemplated hereby are consummated as originally  contemplated to
the greatest extent possible.

9.8  Assignment.  Neither  this  Agreement  nor any of the rights,  interests or
obligations  hereunder shall be assigned by any of the parties hereto,  in whole
or in part (whether by operation of law or otherwise), without the prior written
consent of the other party, and any attempt to make any such assignment  without
such consent  shall be null and void.  Subject to the preceding  sentence,  this
Agreement  will be binding upon,  inure to the benefit of and be  enforceable by
the parties and their respective successors and assigns.

9.9  Submission to  Jurisdiction;  Waivers.  Each of Valero and UDS  irrevocably
agrees that any legal action or proceeding with respect to this Agreement or for
recognition  and  enforcement  of any judgment in respect  hereof brought by the
other party hereto or its successors or assigns may be brought and determined in
the Chancery or other  Courts of the State of  Delaware,  and each of Valero and
UDS hereby irrevocably  submits with regard to any such action or proceeding for
itself and in respect to its  property,  generally and  unconditionally,  to the
nonexclusive jurisdiction of the aforesaid courts. Each of Valero and UDS hereby
irrevocably  waives,  and agrees not to assert,  by way of motion, as a defense,
counterclaim  or  otherwise,  in any action or  proceeding  with respect to this
Agreement,  (a) any claim that it is not personally  subject to the jurisdiction
of the  above-named  courts for any reason  other than the  failure to  lawfully
serve process, (b) that it or its property is exempt or immune from jurisdiction
of any such court or from any legal  process  commenced in such courts  (whether
through service of notice,  attachment  prior to judgment,  attachment in aid of
execution of judgment,  execution of judgment or otherwise),  (c) to the fullest
extent  permitted by applicable law, that (i) the suit,  action or proceeding in
any such court is brought in an inconvenient forum, (ii) the venue of such suit,
action or proceeding is improper and (iii) this Agreement, or the subject matter
hereof, may not be enforced in or by such courts and (d) any right to a trial by
jury.

9.10 Enforcement.  The parties hereto agree that irreparable  damage would occur
in the event that any of the  provisions of this Agreement were not performed in
accordance with their specific terms. It is accordingly  agreed that the parties
hereto shall be entitled to specific performance of the terms hereof, this being
in addition to any other remedy to which they are entitled at law or in equity.



                  IN WITNESS WHEREOF,  Valero and UDS have caused this Agreement
to be signed by their respective  officers thereunto duly authorized,  all as of
the date first written above.

                            VALERO ENERGY CORPORATION



                            By:  /s/ William E. Greehey
                            Name:    William E. Greehey
                            Title:   Chief Executive Officer and President


                            ULTRAMAR DIAMOND SHAMROCK CORPORATION



                            By:  /s/ Jean R. Gaulin
                            Name:    Jean R. Gaulin
                            Title:   Chief Executive Officer and President