FIRST AMENDMENT TO REVOLVING
                                CREDIT AGREEMENT


         THIS  FIRST  AMENDMENT  TO  REVOLVING  CREDIT  AGREEMENT  (this  "First
Amendment") is made and entered into as of the 28th day of January, 1998, by and
among MASTEC,  INC., a Delaware  corporation  (the "Parent"),  its  Subsidiaries
(other than Excluded Subsidiaries and members of the MasTec International Group)
listed on Schedule 1 to the Credit  Agreement  defined below  (together with the
Parent,  collectively  the  "Borrowers"),   TELE-COMMUNICATIONS  CORPORATION  OF
VIRGINIA,  a  Virginia  corporation,  E. L.  DALTON  &  COMPANY,  INC.,  a Texas
corporation,   NORTHLAND  CONTRACTING,  INC.,  a  Minnesota  corporation,  WILDE
CONSTRUCTION,  INC., a Minnesota  corporation,  WILDE OPTICAL  SERVICE,  INC., a
Minnesota  corporation,  WILDE  ACQUISITION  CO., INC., a Delaware  corporation,
WILDE HOLDING CO., INC., a Delaware  corporation,  WEEKS CONSTRUCTION COMPANY, a
North  Carolina  corporation,  AIDCO,  INC.,  a  California  corporation,  AIDCO
SYSTEMS,  INC., a California  corporation,  and G.J.S.  CONSTRUCTION COMPANY, an
Arizona corporation,  (collectively,  the "New U.S. Subsidiaries"),  BANKBOSTON,
N.A.,  CREDITANSTALT-BANKVEREIN,  FIRST  UNION  NATIONAL  BANK OF  FLORIDA,  THE
SUMITOMO  BANK,  LIMITED,  SCOTIABANC  INC.,  THE FUJI BANK AND  TRUST  COMPANY,
COMERICA BANK and LTCB TRUST COMPANY (collectively, the "Banks") and BANKBOSTON,
N.A. as agent (the "Agent") for the Banks.

         WHEREAS,  the  Borrowers,  the  Banks  and  the  Agent  entered  into a
Revolving  Credit  Agreement dated as of June 9, 1997 (the "Credit  Agreement"),
pursuant to which the Banks  extended  credit to the  Borrowers on the terms set
forth therein;

         WHEREAS,  the Parent has informed the Banks that it has acquired all of
the capital stock of  Tele-Communications  Corporation of Virginia, E. L. Dalto
& Company,  Inc., Northland Contracting,  Inc., Wilde Construction,  Inc., Wilde
Optical Service, Inc., Weeks Construction  Company,  Aidco, Inc., Aidco Systems,
Inc., G.J.S.  Construction  Company,  and E.L. Dalton Equipment Co., Inc., a 
Texas corporation, and has formed Wilde Acquisition Co., Inc. and Wilde Holding
Co., Inc.;

         WHEREAS,  the Parent has informed the Banks that E.L. Dalton  Equipment
Co.,  Inc. has merged into E. L. Dalton & Company, Inc., Burnup & Sims TSI, Inc.
has merged into Shanco Corporation,  and  Harrison-Wright  Co., Inc. has merged 
into Burnup & Sims of the Carolinas, Inc.(surviving as "Harrison-Wright Co., 
Inc.");

         WHEREAS, it is a condition to the Credit Agreement that the New U.S. 
Subsidiaries become parties to the Credit Agreement; and

         WHEREAS,  the parties desire to amend the Credit Agreement to make the
New U.S.  Subsidiaries parties thereto on the terms set
forth herein;

         NOW, THEREFORE,  in consideration of the foregoing,  and for other good
and  valuable  consideration,  the receipt and  sufficiency  of which are hereby
acknowledged, the parties agree to amend the Credit Agreement as follows:

         1.       Definitions.  Capitalized terms used herein without definition
shall have the meanings assigned to such terms in the Credit Agreement.

         2.  Amendments to the Credit Agreement.  As of the Effective Date (as 
hereinafter defined):

                  (a) Schedule 1 to the Credit  Agreement  is hereby  amended by
         deleting such Schedule 1 in its entirety and  substituting the Schedule
         1 attached hereto in place thereof.  Each of the New U.S.  Subsidiaries
         agrees that it has the rights and  obligations  of a Borrower under the
         Credit Agreement and shall be liable under the Notes as a Borrower.

                  (b) Section 4.13 of the Credit  Agreement is hereby amended by
         deleting the second  sentence in its entirety and  substituting  in its
         place  thereof  the  following:  "Any  Subsidiary  which is required to
         become a  Borrower  pursuant  to the terms of this  ss.4.13  shall sign
         Notes, shall enter into a joinder and affirmation to this Agreement and
         the U.S. Stock Pledge Agreement in substantially  the form of Exhibit F
         attached hereto  providing that such Subsidiary shall become a Borrower
         hereunder,  and shall provide such other documentation as the Agent may
         reasonably request, including,  without limitation,  documentation with
         respect to conditions specified in ss.9 hereof."

                  (c) Section  7.4(c) of the Credit  Agreement is hereby amended
         by  inserting  the  phrase  ",  such  contingent  payments  to  include
         non-compete   agreements"  immediately  before  the  close  parenthesis
         thereof.

                  (d) Section 11 of the Credit  Agreement  is hereby  amended by
         adding the  following at the end of the paragraph  thereof:  "The Agent
         may from time to time, in its discretion, release Collateral,  provided
         that the aggregate  value of such released  Collateral  does not exceed
         five  percent  (5%) of the  consolidated  net  worth  of the  Borrowers
         determined in accordance with GAAP."

                  (e) Exhibit F is hereby  added to the Credit  Agreement in the
         form attached hereto.

         3.  Effectiveness.  This First  Amendment  shall be effective as of the
date hereof,  subject to the receipt by the Agent of this First  Amendment  duly
and properly authorized, executed and delivered by the respective parties hereto
(such date being  referred to as the  "Effective  Date").  This First  Amendment
shall become effective upon satisfaction of each of the following conditions:

                  (a)      This First Amendment shall have been executed and 
         delivered by the respective parties hereto;

                  (b)  The  New  U.S.   Subsidiaries  shall  have  executed  and
         delivered to the Agent allonges to the Notes  reflecting their addition
         as Borrowers described in ss.2 of this First Amendment;

                  (c) The New U.S.  Subsidiaries  shall  have  delivered  to the
         Agent certified copies of corporate resolutions of each of the New U.S.
         Subsidiaries satisfactory to the Agent authorizing this First Amendment
         and all related documents;

                  (d) Each of E. L. Dalton & Company,  Inc., Shanco  Corporation
         and Harrison-Wright  Co., Inc. shall have delivered to the Agent copies
         of certificates  and/or plans of merger filed with its charter or other
         incorporation documents, certified by the Secretary of State of each of
         their jurisdictions of incorporation; and

                  (e)   The   Parent,   Harrison-Wright   Co.,   Inc.,   Latlink
         Corporation,  MasTec International,  Inc., Wilde Acquisition Co., Inc.,
         Wilde Holding Co., Inc. and Aidco,  Inc. (the  "Pledgors")  and the New
         U.S.  Subsidiaries  shall have  executed  and  delivered to the Agent a
         First  Amendment to U.S. Stock Pledge  Agreement and the Pledgors shall
         have delivered any and all stock  certificates  representing  shares of
         stock in the New U.S.  Subsidiaries to the Agent, together with undated
         stock powers related thereto.

         4.  Representations and  Warranties.  Each of the Borrowers (including,
without limitation, the New U.S. Subsidiaries) represents and warrants as 
follows:

                  (a) The  execution,  delivery and  performance of each of this
         First Amendment,  the First Amendment to U.S. Stock Pledge Agreement of
         even date  herewith,  the Credit  Agreement  and the U.S.  Stock Pledge
         Agreement dated of June 9, 1997, among the Parent, Burnup & Sims of the
         Carolinas,  Inc., Latlink Corporation,  MasTec International,  Inc. and
         the Agent,  each as amended as of the date hereof and the  transactions
         contemplated  hereby and  thereby  are within the  corporate  power and
         authority  of such  Borrower  and have  been or will be  authorized  by
         proper  corporate  proceedings,  and do not (a)  require any consent or
         approval of the  stockholders  of such  Borrower,  (b)  contravene  any
         provision of the charter  documents or by-laws of such  Borrower or any
         law, rule or regulation  applicable to such Borrower, or (c) contravene
         any provision of, or constitute an event of default or event which, but
         for the requirement that time elapse or notice be given, or both, would
         constitute an event of default  under,  any other  material  agreement,
         instrument or undertaking binding on such Borrower.

                  (b) This First  Amendment,  the First  Amendment to U.S. Stock
         Pledge Agreement of even date herewith, the U.S. Stock Pledge Agreement
         and the Credit  Agreement  as amended as of the date  hereof and all of
         the terms and  provisions  hereof and thereof are the legal,  valid and
         binding  obligations of such Borrower  enforceable  in accordance  with
         their  respective  terms except as limited by  bankruptcy,  insolvency,
         reorganization,  moratorium or other laws affecting the  enforcement of
         creditors'  rights  generally,  and  except as the  remedy of  specific
         performance or of injunctive relief is subject to the discretion of the
         court before which any proceeding therefor may be brought.

                  (c) The  execution,  delivery  and  performance  of this First
         Amendment,  the First Amendment to U.S. Stock Pledge  Agreement of even
         date herewith, the U.S. Stock Pledge Agreement and the Credit Agreement
         as amended  as of the date  hereof  and the  transactions  contemplated
         hereby and thereby do not require any approval or consent of, or filing
         or registration with, any governmental or other agency or authority, or
         any other party.

                  (d) The representations and warranties  contained in Section 5
         of the Credit  Agreement are true and correct in all material  respects
         as of the date hereof as though made on and as of the date hereof.

                  (e) No Default or Event of Default under the Credit  Agreement
         has occurred and is continuing.

         5.  Ratification,  etc. Except as expressly amended hereby,  the Credit
Agreement,  the  other  Loan  Documents  and  all  documents,   instruments  and
agreements related thereto are hereby ratified and confirmed in all respects and
shall  continue in full force and effect.  This First  Amendment  and the Credit
Agreement shall hereafter be read and construed  together as a single  document,
and  all  references  in the  Credit  Agreement  or  any  related  agreement  or
instrument to the Credit Agreement shall hereafter refer to the Credit Agreement
as amended by this First Amendment.

         6.  GOVERNING  LAW.  THIS  FIRST  AMENDMENT  SHALL BE  GOVERNED  BY AND
CONSTRUED IN ACCORDANCE WITH THE LAWS OF THE COMMONWEALTH OF  MASSACHUSETTS  AND
SHALL TAKE EFFECT AS A SEALED INSTRUMENT IN ACCORDANCE WITH SUCH LAWS.

         7. Counterparts.  This First Amendment may be executed in any number of
counterparts and by different parties hereto on separate  counterparts,  each of
which when so executed  and  delivered  shall be an  original,  but all of which
counterparts  taken  together  shall be  deemed to  constitute  one and the same
instrument.





         IN WITNESS  WHEREOF,  each of the  undersigned  have duly executed this
First Amendment under seal as of the date first set forth above.

                                    The Borrowers:

                                    MASTEC, INC.



                                    By:___________________________________
                                        Name:
                                        Title:

                                    B & D CONTRACTORS OF SHELBY, INC.
                                    BURNUP & SIMS OF TEXAS, INC.
                                    HARRISON-WRIGHT CO., INC.
                                    UTILITY PRECAST, INC.
                                    BURNUP & SIMS TELCOM OF FLORIDA, INC.
                                    CHURCH & TOWER ENVIRONMENTAL, INC.
                                    CHURCH & TOWER FIBER TEL, INC.
                                    CHURCH & TOWER, INC.
                                    CHURCH & TOWER OF FLORIDA, INC.
                                    CHURCH & TOWER OF TN, INC.
                                    DESIGNED TRAFFIC INSTALLATION CO.
                                    GDSI, INC.
                                    KENNEDY CABLE CONSTRUCTION, INC.
                                    LATLINK CORPORATION
                                    LATLINK ARGENTINA, INC.
                                    MASTEC COMTEC OF CALIFORNIA, INC.
                                    MASTEC COMTEC OF THE CAROLINAS, INC.
                                    MASTEC TECHNOLOGIES, INC.
                                    MASTEC TELEPORT, INC.
                                    R.D. MOODY & ASSOCIATES, INC.
                                    R.D. MOODY AND ASSOCIATES, INC. OF  VIRGINIA
                                    SHANCO CORPORATION
                                    UTILITY LINE MAINTENANCE, INC.



                                    By:___________________________________
                                        Name:
                                        Title:






                                    The New U.S. Subsidiaries:

                                    AIDCO, INC.
                                    AIDCO SYSTEMS, INC.
                                    E. L. DALTON & COMPANY, INC.
                                    NORTHLAND CONTRACTING, INC.
                                    WILDE CONSTRUCTION, INC.
                                    WILDE OPTICAL SERVICE, INC.
                                    TELE-COMMUNICATIONS CORPORATION  OF VIRGINIA
                                    WILDE ACQUISITION CO., INC.
                                    WILDE HOLDING CO., INC.
                                    WEEKS CONSTRUCTION COMPANY
                                    G.J.S. CONSTRUCTION COMPANY



                                    By:___________________________________
                                        Name:
                                        Title:








                                    The Banks:

                                    CREDITANSTALT-BANKVEREIN



                                    By:___________________________________
                                        Name:
                                        Title:



                                    By:___________________________________
                                        Name:
                                        Title:

                                    FIRST UNION NATIONAL BANK OF FLORIDA



                                    By:___________________________________
                                        Name:
                                        Title:

                                    THE SUMITOMO BANK, LIMITED



                                    By:___________________________________
                                        Name:
                                        Title:



                                    By:___________________________________
                                        Name:
                                        Title:







                                    SCOTIABANC INC.



                                    By:___________________________________
                                        Name:
                                        Title:

                                    THE FUJI BANK AND TRUST COMPANY



                                    By:___________________________________
                                        Name:
                                        Title:

                                    COMERICA BANK



                                    By:___________________________________
                                        Name:
                                        Title:

                                    LTCB TRUST COMPANY



                                    By:___________________________________
                                        Name:
                                        Title:

                                    BANKBOSTON, N.A.,
                                      individually and as Agent



                                    By:___________________________________
                                        Name:
                                        Title:





                                                                 - 9 -

*Corporation's stock to be pledged
*Corporation's stock to be pledged
BOS-BUSN:511686.1
                                   SCHEDULE 1


I.       U.S. SUBSIDIARIES


         A.       BORROWERS

         *Aidco, Inc.

                                                                                 
         Date of Incorporation:  10/25/91            Stock Information:
         State of Incorporation:  California         Total Shares Authorized Common Stock:
         Address:  12675 Colony Court                         100,000
                   Chino, CA  91710                  Par Value:  None
                                                     No. Issued & Outstanding:  3,000
                                                     Owner:  MasTec, Inc.


         *Aidco Systems, Inc.

         Date of Incorporation:  7/26/93             Stock Information:
         State of Incorporation:  California         Total Shares Authorized Common Stock:
         Address:  12675 Colony Court                         100,000
                   Chino, CA  91710                  Par Value:  None
                                                     No. Issued & Outstanding:  1,000
                                                     Owner:  MasTec, Inc.


         *B & D Contractors of Shelby, Inc.

         Date of Incorporation:  6/26/81             Stock Information:
         State of Incorporation:  North Carolina     Total Shares Authorized Common Stock:
         Address:  1528 McCracken Drive                       1,000
                   Shelby, NC  28150                 Par Value:  $100.00
                                                     No. Issued & Outstanding:  100
                                                     Owner:  MasTec, Inc.


         *Burnup & Sims Telcom of Florida, Inc.

         Date of Incorporation:  8/18/94             Stock Information:
         State of Incorporation:  Florida            Total Shares Authorized Common Stock: 
         Address:  7221 Dr. Martin Luther Jr. Blvd E.         1,000
                   Tampa, FL  33519                  Par Value:  $.01
                   (813) 621-0881                    No. Issued & Outstanding:  100
                   (813) 626-3740 - Fax              Owner:  MasTec, Inc.
                   (800) 282-2939


         *Burnup & Sims of Texas, Inc.

         Date of Incorporation:  8/1/58              Stock Information:
         State of Incorporation:  Texas              Total Shares Authorized Common Stock:
         Address:  2716 East Fifth                            10,000
                   Austin, TX  78702                 Par Value:  $100.00
                   (512) 476-6777                    No. Issued & Outstanding:  700
                   (512) 476-6777                    Owner:  MasTec, Inc.
                   (800) 252-5471
         Address:  P.O. Box
                   Austin, Texas  78767


         *Church & Tower, Inc.

         Date of Incorporation:  8/22/90             Stock Information:
         State of Incorporation:  Florida            Total Shares Authorized Common Stock:
         Address:  3155 NW 77th Avenue                        5,000
                   Miami, FL 33122                   Par Value:  $1.00
                                                     No. Issued & Outstanding:  1000
                                                     Owner:  MasTec, Inc.


         *Church & Tower Environmental, Inc.

         Date of Incorporation:  7/16/96             Stock Information:
         State of Incorporation:  Delaware           Total Shares Authorized Common Stock:
         Address:  3155 NW 77th Ave.                          1,000
                   Miami, FL 33122                   Par Value:  $.01
                                                     No. Issued & Outstanding:  100
                                                     Owner:  MasTec, Inc.


         *Church & Tower Fiber Tel, Inc.

         Date of Incorporation:  8/31/94             Stock Information:
         State of Incorporation:  Delaware           Total Shares Authorized Common Stock:
         Address:  4598 Stonegate Industrial Blvd.#B          1,000
                   Stone Mountain Georgia 30078      Par Value:  $.01
                   (404) 508-1666                    No. Issued & Outstanding:  200
                   (404) 508-0106-FAX                Owner:  MasTec, Inc.


         *Church & Tower of Florida, Inc.

         Date of Incorporation:  9/19/68             Stock Information:
         State of Incorporation:  Florida            Total Shares Authorized Common Stock:
         Address:  3155 NW 77th Avenue                        10,000
                    Miami, FL 33122                  Par Value:  $10.00
                                                     No. Issued & Outstanding:  100
                                                     Owner:  MasTec, Inc.


         *Church & Tower of TN, Inc.

         Date of Incorporation:  7/25/79             Stock Information:
         State of Incorporation:  Delaware           Total Shares Authorized Common Stock:
         Address:  3155 NW 77th Avenue                        100
                   Miami, FL 33122                   Par Value:  $1.00
                   (305) 599-1800                    No. Issued & Outstanding:  100
                                                     Owner:  MasTec, Inc.


         *Designed Traffic Installation Co.

         Date of Incorporation:  3/8/65              Stock Information:
         State of Incorporation:  Florida            Total Shares Authorized Common Stock:
         Address:  2801 SW 46th Ave                           10,000
                   Ft. Lauderdale, FL 33314          Par Value:  $10.00
                   (305) 587-1700                    No. Issued & Outstanding:  6,000
                   (305) 587-4070 - Fax            Owner:  MasTec, Inc.


         *E. L. Dalton & Company, Inc.

         Date of Incorporation:  9/18/72             Stock Information:
         State of Incorporation:  Texas              Total Shares Authorized Common Stock:
         Address:  8700 Stemmons Fwy., Suite 125              100,000
                   Dallas, TX  75247                 Par Value:  $1.00
                                                     No. Issued & Outstanding:  2,000
                                                     Owner:  MasTec, Inc.


         *GDSI, Inc.

         Date of Incorporation:  12/24/80            Stock Information:
         State of Incorporation:  Delaware           Total Shares Authorized Common Stock:
         Address:  5555 Oakbrook Way Ste. 620                 100
                   Norcross, GA  30093-22770         Par Value:  $1.00
                   (770) 662-8310                    No. Issued & Outstanding:  100
                   (770) 242-7680 - Fax              Owner:  MasTec, Inc.


         *G.J.S. Construction Company
         (d/b/a Somerville Construction Co.)

         Date of Incorporation:  6/22/92             Stock Information:
         State of Incorporation:  Arizona            Total Shares Authorized Common Stock:
         Address:  3806 S. 16th Street                                 3,000,000
                     Phoenix, AZ  85040              Par Value:  $1.00
                                                     No. Issued & Outstanding:  175,100
                                                     Owner:  MasTec, Inc.


         *Harrison-Wright Co., Inc.
         (formerly known as BURNUP & SIMS OF THE CAROLINAS, INC.)

         Date of Incorporation:  2/18/71             Stock Information:
         State of Incorporation:  Delaware           Total Shares Authorized Common Stock:
         Address:  3133 Cedar Park Rd.                        10,000
                   Greensboro, NC 27405              Par Value:  $1.00
                                                     No. Issued & Outstanding:  200
                                                     Owner:  MasTec, Inc.


         *Kennedy Cable Construction, Inc.

         Date of Incorporation:  1/24/97             Stock Information:
         State of Incorporation:  Delaware           Total Shares Authorized Common Stock:
         Address:  Highway 280 West                           1,000
                     Reidsville, GA 30453            Par Value:  $.01
                     (912) 557-4751                  No. Issued & Outstanding:  100
                     (912) 557-6545                  Owner:  MasTec, Inc.


         *Latlink Corporation

         Date of Incorporation:  11/16/95            Stock Information:
         State of Incorporation:  Delaware           Total Shares Authorized Common Stock:
         Address:  3155 NW 77th Ave.                          2,500
                   Miami, FL 33122                   Par Value:  $.01
                                                     No. Issued & Outstanding:  100
                                                     Owner:  MasTec, Inc.


         *Latlink Argentina, Inc.
         (originally MasTec Equipment, Inc.  Name changes: MasTec Offshore, Inc., Latlink, Inc., Latlink Argentina, Inc.)

         Date of Incorporation:  7/1/94              Stock Information:
         State of Incorporation:  Delaware           Total Shares Authorized Common Stock:
         Address:  3155 NW 77th Ave.                          2,500
                   Miami, FL 33122                   Par Value:  $.01
                                                     No. Issued & Outstanding:  100
                                                     Owner:  Latlink Corporation


         *MasTec Comtec of California, Inc.

         Date of Incorporation:  7/25/79             Stock Information:
         State of Incorporation:  Delaware           Total Shares Authorized Common Stock:
         Address:  15119 Arrow Highway                        100
                   Irwindale, CA 91706               Par Value:  $1.00
                   (818) 877-2700                    No. Issued & Outstanding:  100
                   (818) 960-4166 - FAX              Owner:  MasTec, Inc.


         *MasTec Comtec of the Carolinas, Inc.

         Date of Incorporation:  9/24/79             Stock Information:
         State of Incorporation:  Delaware           Total Shares Authorized Common Stock:
         Address:  1715 Orr Industrial Court                  10,000
                   Charlotte, NC 28213               Par Value:  $.01
                   (770) 598-9229                    No. Issued & Outstanding:  2100
                   (770) 596-8254                    Owner:  MasTec, Inc.


         *MasTec Technologies, Inc.

         Date of Incorporation:  7/31/95             Stock Information:
         State of Incorporation:  Delaware           Total Shares Authorized Common Stock:
         Address:  8600 N.W. 36th Street                      1,000
                     Miami, FL 33166                 Par Value:  $.01
                                                     No. Issued & Outstanding:  100
                                                     Owner:  MasTec, Inc.


         *MasTec Teleport, Inc.

         Date of Incorporation:  2/13/95             Stock Information:
         State of Incorporation:  Florida            Total Shares Authorized Common Stock:
         Address:  3155 NW 77th Avenue                        5,000
                   Miami, FL  33122                  Par Value:  $1.00
                   (305) 599-1800                    No. Issued & Outstanding:  1,000
                                                     Owner:  MasTec, Inc. -- 750 shares


         *Northland Contracting, Inc.

         Date of Incorporation:  6/4/79              Stock Information:
         State of Incorporation:  Minnesota          Total Shares Authorized Common Stock:
         Address:  Highway #2 East                            2,500
                   Shevlin, MN  56676                Par Value:  $.01
                                                     No. Issued & Outstanding:  100
                                                     Owner:  Wilde Acquisition Co., Inc.

         *R.D. Moody & Associates, Inc.

         Date of Incorporation:  2/18/88             Stock Information:
         State of Incorporation:  Florida            Total Shares Authorized Common Stock:
         Address:  5380 Capital Circle, NW                    5,000
                   Tallahassee, FL 32303             Par Value:  $1.00
                                                     No. Issued & Outstanding:  500
                                                     Owner:  MasTec, Inc.


         *R.D. Moody and Associates, Inc. of Virginia

         Date of Incorporation:  9/20/94             Stock Information:
         State of Incorporation:  Virginia           Total Shares Authorized Common Stock:
         Address:  5380 Capital Circle, NW                    5,000
                   Tallahassee, FL 32303             Par Value:  $20.00
                                                     No. Issued & Outstanding:  5000
                                                     Owner:  MasTec, Inc.


         *Shanco Corporation

         Date of Incorporation:  2/4/97              Stock Information:
         State of Incorporation:  Florida            Total Shares Authorized Common Stock:
         Address:  14170 Jetport Loop                         1,000
                   Fort Myers FL 33913               Par Value:  $.01
                   (941) 768-5001                    Issued & Outstanding:  300
                   (941) 768-0035 (FAX)              Owner:  MasTec, Inc.


         *Tele-Communications Corporation of Virginia

         Date of Incorporation:  10/15/82            Stock Information:
         State of Incorporation:  Virginia           Total Shares Authorized Common Stock:
         Address:  1868 Mount Pleasant Road                   20,000
                   Chesapeake, VA  23322             Par Value:  $1.00
                                                     No. Issued & Outstanding:  18,950
                                                     Owner:  MasTec, Inc.


         *Utility Line Maintenance

         Date of Incorporation:  8/17/88             Stock Information:
         State of Incorporation:  Georgia            Total Shares Authorized Common Stock:
         Address:  1696 N. Georgia Hwy. 16                    1,000,000
                   Whitesburg, GA 30185              Par Value:  $1.00
                   (770)832-1604                     No. Issued & Outstanding:  500
                   (770) 832-9738                    Owner:  MasTec, Inc.


         *Utility Precast,  Inc., a Delaware corporation  (formerly known as H-W
         Acquisition III Co., Inc.)

         Date of Incorporation:  10/17/96            Stock Information:
         State of Incorporation:  Delaware           Total Shares Authorized Common Stock:
         Address:  3133 Cedar Park Road                       1,000
                   Greensboro, NC  27405             Par Value:  $.01
                   (910) 697-2930                    No. Issued & Outstanding:  100
                   (910) 697-7895 (fax)              Owner:  Harrison-Wright Co., Inc.


         *Weeks Construction Company

         Date of Incorporation:  4/27/79             Stock Information:
         State of Incorporation:  North Carolina     Total Shares Authorized Common Stock:
         Address:  1602 East Dixie Drive                      100,000
                   Asheboro, NC  27204               Par Value:  $1.00
                                                     No. Issued & Outstanding:  439
                                                     Owner:  MasTec, Inc.







         *Wilde Acquisition Co., Inc.

         Date of Incorporation:  7/31/97             Stock Information:
         State of Incorporation:  Delaware           Total Shares Authorized Common Stock:
         Address:  3155 NW 77th Avenue                        1,000
                   Miami, FL  33122                  Par Value:  $.01
                                                     No. Issued & Outstanding:  100
                                                     Owner:  Wilde Holding Co., Inc.


         *Wilde Holding Co., Inc.

         Date of Incorporation:  5/30/95             Stock Information:
         State of Incorporation:  Delaware           Total Shares Authorized Common Stock:
         Address:  3155 NW 77th Avenue                        1,000
                   Miami, FL  33122                  Par Value:  $.01
                                                     No. Issued & Outstanding:  100
                                                     Owner:  MasTec, Inc.


         *Wilde Construction, Inc.

         Date of Incorporation:  9/26/74             Stock Information:
         State of Incorporation:  Minnesota          Total Shares Authorized Common Stock:
         Address:  Highway #2 East                            750
                   Shevlin, MN  56676                Par Value:  $.01
                                                     No. Issued & Outstanding:  60
                                                     Owner:  MasTec, Inc.


         *Wilde Optical Service, Inc.

         Date of Incorporation:  2/9/87              Stock Information:
         State of Incorporation:  Minnesota          Total Shares Authorized Common Stock:
         Address:  Highway #2 East                            10,000
                   Shevlin, MN  56676                Par Value:  $.01
                                                     No. Issued & Outstanding:  1,000
                                                     Owner:  MasTec, Inc.


         B.       NON-BORROWERS

                  1.       EXCLUDED SUBSIDIARIES

                  Burnup & Sims Network Designs, Inc.
                  Floyd Theatres, Inc.
                  Tallahassee Theatres, Inc.
                  Haven Outdoor Drive-Theatre, Inc.
                  Burnup & Sims Enterprises, Inc.
                  Burnup & Sims of Mississippi, Inc.
                  Burnup & Sims Communications Services of Florida, Inc.
                  Cal Technical Services, Inc.
                  Capscan Cable Company, Inc.
                  DTI, Inc.
                  Excom Realty, Inc.
                  Gasco, Inc.
                  GCC Corp.
                  L.P. & H.
                  MasTec Angola, Inc.
                  MasTec - Haiti, Inc.
                  MasTec - Puerto Rico, Inc.
                  MasTec Wireless, Inc.
                  Pantel International, Inc. - Hungary
                  Telink, Inc.
                  9001 Joint Venture
                  H-W Acquisition II, Inc.
                  MasTec Telepub, Inc.


                  2.       U.S. MEMBERS OF THE MASTEC INTERNATIONAL GROUP

                  *MasTec International, Inc.

                  Date of Incorporation:  4/22/92    Stock Information:
                  State of Incorporation:  Delaware  Total Shares Authorized Common Stock:
                  Address:  3155 NW 77th Avenue               1,000
                            Miami, FL 33122          Par Value:  $.01
                                                     No. Issued & Outstanding:  1,000
                                                     Owner:  MasTec, Inc.


                  *MasTec Latin America, Inc.

                  Date of Incorporation:  2/13/97    Stock Information:
                  State of Incorporation:  Delaware  Total Shares Authorized Common Stock:
                  Address:  3155 NW 77th Avenue               1,000
                            Miami, FL  33122         Par Value:  $.01
                            (305) 599-1800           No. Issued & Outstanding:  100
                                                     Owner:  MasTec International, Inc.


II.      SINTEL GROUP (NON-BORROWERS)

         *Sistemas e Instalaciones de Telecomunicaciones, S.A.

         Date of Incorporation:  2/8/50              Stock Information:
         Country of Incorporation:  Spain            Total Shares Authorized Common Stock:
         Address:  C/.del Arte.21 28033                       6,100,000
                   Madrid, Spain                     Par Value:  1,000 Pesetas
                                                     No. Issued & Outstanding:  6,100,000
                                                     Owner:  MasTec International, Inc.


         Sintel - Peru, S.A.
         Sintel - Venezuela, S.A.
         Sintelar, S.A.
         Sietel, S.A.







                                                                  -3-


BOS-BUSN:511686.1
                                                                       EXHIBIT F

                                     FORM OF
                        JOINDER AGREEMENT AND AFFIRMATION


         This Joinder  Agreement and Affirmation  (this "Joinder  Agreement") is
executed and  delivered by [Name of Newly  Acquired  Subsidiary]  (the "New U.S.
Subsidiary")  pursuant to ss.4.13 of the Revolving  Credit Agreement dated as of
June 9, 1997,  as may be amended  from time to time,  (the  "Credit  Agreement")
among MasTec,  Inc., a Delaware  corporation  (the "Parent"),  its  Subsidiaries
(other than Excluded Subsidiaries and members of the MasTec International Group)
listed  on  Schedule  1 to the  Credit  Agreement  (together  with  the  Parent,
collectively the "Borrowers") BankBoston, N.A., Creditanstalt-Bankverein,  First
Union National Bank of Florida, The Sumitomo Bank, Limited, Scotiabanc Inc., The
Fuji Bank and Trust Company, Comerica Bank and LTCB Trust Company (collectively,
the "Banks") and BankBoston,  N.A. as agent (the "Agent") for the Banks, and any
other  financial  institutions  which become parties to the Credit  Agreement in
accordance with ss.ss.14 and 17 of the Credit  Agreement.  All capitalized terms
used in this Joinder  Agreement and not otherwise  defined herein shall have the
same meanings herein as in the Credit Agreement.

         The New U.S.  Subsidiary  hereby agrees to become a Borrower in respect
of the  Obligations  as set forth in the Credit  Agreement and, by executing and
delivering  this Joinder  Agreement,  does hereby join and become a party to the
Credit Agreement as a Borrower,  assuming all of the obligations and liabilities
of a Borrower thereunder.  The New U.S. Subsidiary agrees to comply with, and be
bound  by,  all of the terms  and  conditions  of the  Credit  Agreement  in all
respects as an original Borrower thereunder,  as if the New U.S. Subsidiary were
an original  signatory  thereto,  including  without  limitation,  assuming  all
obligations and liabilities  arising or incurred under the Credit  Agreement and
the Notes on and after the Closing Date.

         To the extent that the New U.S.  Subsidiary holds any stock of any U.S.
Subsidiary  (other  than the  stock  of an  Excluded  Subsidiary),  the New U.S.
Subsidiary  hereby  agrees  to pledge  all such  stock  and,  by  executing  and
delivering  this Joinder  Agreement,  does hereby join and become a party to the
U.S.  Stock Pledge  Agreement  dated as of June 9, 1997,  as may be amended from
time to time, (the "U.S. Stock Pledge") among MasTec, Inc., Burnup & Sims of the
Carolinas, Inc., Latlink Corporation, MasTec International, Inc. and BankBoston,
N.A. as Agent for the Banks, as an original Pledgor thereunder,  assuming all of
the obligations and liabilities of a Pledgor thereunder. The New U.S. Subsidiary
agrees to comply with,  and be bound by, all of the terms and  conditions of the
U.S. Stock Pledge in all respects as an original Pledgor  thereunder,  as if the
New U.S.  Subsidiary  were an  original  signatory  thereto,  including  without
limitation,  assuming all obligations and liabilities  arising or incurred under
the U.S. Stock Pledge on and after the Closing Date.

         The New U.S.  Subsidiary  hereby  consents to and agrees to be bound by
the provisions of ss.ss.4.1, 6 and 7 of the U.S. Stock Pledge, and hereby agrees
to cooperate fully and in good faith with the Agent and the Pledgors in carrying
out such  provisions  and, by executing and delivering  this Joinder  Agreement,
does hereby join the U.S. Stock Pledge to the extent stated.

         Without  limiting the above, the New U.S.  Subsidiary  hereby expressly
consents to the terms and  conditions  of ss.22 (Waiver of Jury Trial) and ss.23
(Governing Law;  Submission to Jurisdiction) of the Credit Agreement,  and ss.18
(Waiver of Jury Trial) and ss.17 (Governing Law; Consent to Jurisdiction) of the
Credit Agreement.

         The undersigned  agrees that this Joinder  Agreement shall be deemed to
be, and is hereby made a part of, the Credit  Agreement as if set forth  therein
in full.






         IN WITNESS WHEREOF,  the undersigned has caused this Joinder  Agreement
to be duly executed on this ___ day of _________ 199__.


                                       [NEW U.S. SUBSIDIARY]


                                       By:      _________________________
                                                Name:
                                                Title:

                                       Address for Notices:
                                       [Address]


Except as  expressly  modified  hereby,  the  Credit  Agreement,  the other Loan
Documents and all  documents,  instruments  and agreements  related  thereto are
hereby  ratified and confirmed in all respects and shall  continue in full force
and effect.  The  Borrowers  hereby  affirm their  Obligations  under the Credit
Agreement and agree that they are jointly and severally liable with the New U.S.
Subsidiary with respect to the Total Commitment.

Agreed to and Consented by:

 MASTEC, INC.

By:___________________________________
     Name:
     Title:

[SUBSIDIARY]
[SUBSIDIARY]
[SUBSIDIARY]
[SUBSIDIARY]
[SUBSIDIARY]
[SUBSIDIARY]

By:___________________________________
     Name:
     Title: