13 of 13
                                FORM 10-Q


                    SECURITIES AND EXCHANGE COMMISSION
                         WASHINGTON, D.C.  20549

(Mark One)

(X)  QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d)
     OF THE SECURITIES EXCHANGE ACT OF 1934

For the quarterly period ended March 31, 2001

                                    OR

( )  TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d)
     OF THE SECURITIES EXCHANGE ACT OF 1934

For the transition period from ________________ to ________________

Commission file number 0-19601


         SOUTHWEST ROYALTIES INSTITUTIONAL 1990-91 INCOME PROGRAM
         Southwest Royalties Institutional Income Fund X-B, L.P.
                  (Exact name of registrant as specified
                  in its limited partnership agreement)

Delaware                                75-2332174
(State or other jurisdiction of                (I.R.S. Employer
incorporation or organization)                Identification No.)


                       407 N. Big Spring, Suite 300
                           Midland, Texas 79701
                 (Address of principal executive offices)

                              (915) 686-9927
                      (Registrant's telephone number,
                           including area code)

Indicate  by  check  mark  whether registrant (1)  has  filed  all  reports
required to be filed by Section 13 or 15(d) of the Securities Exchange  Act
of 1934 during the preceding 12 months (or for such shorter period that the
registrant was required to file such reports), and (2) has been subject  to
such filing requirements for the past 90 days:

                            Yes   X   No

        The total number of pages contained in this report is 13.


                     PART I. - FINANCIAL INFORMATION


Item 1.   Financial Statements

The  unaudited  condensed financial statements included  herein  have  been
prepared  by  the Registrant (herein also referred to as the "Partnership")
in  accordance  with generally accepted accounting principles  for  interim
financial information and with the instructions to Form 10-Q and Rule 10-01
of Regulation S-X.  Accordingly, they do not include all of the information
and  footnotes  required  by generally accepted accounting  principles  for
complete   financial  statements.   In  the  opinion  of  management,   all
adjustments necessary for a fair presentation have been included and are of
a  normal  recurring nature.  The financial statements should  be  read  in
conjunction with the audited financial statements and the notes thereto for
the  year ended December 31, 2000 which are found in the Registrant's  Form
10-K  Report  for  2000 filed with the Securities and Exchange  Commission.
The December 31, 2000 balance sheet included herein has been taken from the
Registrant's 2000 Form 10-K Report.  Operating results for the three  month
period  ended March 31, 2001 are not necessarily indicative of the  results
that may be expected for the full year.


         Southwest Royalties Institutional Income Fund X-B, L.P.

                              Balance Sheets


                                                  March 31,     December 31,
                                                     2001           2000
                                                  ---------     ------------
                                                 (unaudited)

  Assets

Current assets:
 Cash and cash equivalents                    $     85,069         80,863
 Receivable from Managing General Partner          116,113        117,172
                                                 ---------      ---------
    Total current assets                           201,182        198,035
                                                 ---------      ---------
Oil and gas properties - using the
 full-cost method of accounting                  3,888,882      3,888,882
  Less accumulated depreciation,
   depletion and amortization                    3,465,853      3,455,853
                                                 ---------      ---------
    Net oil and gas properties                     423,029        433,029
                                                 ---------      ---------
                                              $    624,211        631,064
                                                 =========      =========

  Liabilities and Partners' Equity

Current liability - Distribution payable      $          -              1
                                                 ---------      ---------
Partners' equity:
 General partners                                 (32,000)       (32,315)
 Limited partners                                  656,211        663,378
                                                 ---------      ---------
    Total partners' equity                         624,211        631,063
                                                 ---------      ---------
                                              $    624,211        631,064
                                                 =========      =========


         Southwest Royalties Institutional Income Fund X-B, L.P.

                         Statements of Operations
                               (unaudited)


                                                        Three Months Ended
                                                            March 31,
                                                          2001      2000
                                                          ----      ----
    Revenues

Income from net profits interests                   $   146,261     50,269
Interest                                                  1,044        517
                                                        -------    -------
                                                        147,305     50,786
                                                        -------    -------
    Expenses

General and administrative                               19,157     19,251
Depreciation, depletion and amortization                 10,000      8,000
                                                        -------    -------
                                                         29,157     27,251
                                                        -------    -------
Net income                                          $   118,148     23,535
                                                        =======    =======
Net income allocated to:

 Managing General Partner                           $    11,533      2,838
                                                        =======    =======
 General partner                                    $     1,281        315
                                                        =======    =======
 Limited partners                                   $   105,334     20,382
                                                        =======    =======
  Per limited partner unit                          $      9.42       1.82
                                                        =======    =======


         Southwest Royalties Institutional Income Fund X-B, L.P.

                         Statements of Cash Flows
                               (unaudited)


                                                        Three Months Ended
                                                            March 31,
                                                          2001      2000
                                                          ----      ----

Cash flows from operating activities:

 Cash received from net profits interests           $   147,553     72,315
 Cash paid to suppliers                                (19,390)   (14,540)
 Interest received                                        1,044        517
                                                       --------   --------
  Net cash provided by operating activities             129,207     58,292
                                                       --------   --------
Cash flows used in financing activities:

 Distributions to partners                            (125,001)   (55,038)
                                                       --------   --------

Net increase in cash and cash equivalents                 4,206      3,254

 Beginning of period                                     80,863     20,977
                                                       --------   --------
 End of period                                      $    85,069     24,231
                                                       ========   ========

                                                               (continued)


         Southwest Royalties Institutional Income Fund X-B, L.P.

                   Statements of Cash Flows, continued
                               (unaudited)


                                                        Three Months Ended
                                                            March 31,
                                                          2001      2000
                                                          ----      ----
Reconciliation of net income to net cash
  provided by operating activities:

Net income                                          $   118,148     23,535

Adjustments to reconcile net income to net cash
  provided by operating activities:

  Depreciation, depletion and amortization               10,000      8,000
  Decrease in receivables                                 1,292     22,046
  (Decrease) increase in payables                         (233)      4,711
                                                        -------    -------
Net cash provided by operating activities           $   129,207     58,292
                                                        =======    =======


         Southwest Royalties Institutional Income Fund X-B, L.P.
                     (a Delaware limited partnership)

                      Notes to Financial Statements


1.   Organization
     Southwest  Royalties Institutional Income Fund X-B, L.P. was organized
     under  the laws of the state of Delaware on November 27, 1990 for  the
     purpose  of acquiring producing oil and gas properties and to  produce
     and market crude oil and natural gas produced from such properties for
     a  term  of 50 years, unless terminated at an earlier date as provided
     for  in the Partnership Agreement.  The Partnership sells its oil  and
     gas  production to a variety of purchasers with the prices it receives
     being  dependent  upon the oil and gas economy.  Southwest  Royalties,
     Inc. serves as the Managing General Partner and H. H. Wommack, III, as
     the  individual  general partner.  Revenues, costs  and  expenses  are
     allocated as follows:

                                                     Limited      General
                                                     Partners     Partners
                                                     --------     --------
     Interest income on capital contributions        100%           -
     Oil and gas sales                                90%          10%
     All other revenues                               90%          10%
     Organization and offering costs (1)             100%           -
     Amortization of organization costs              100%           -
     Property acquisition costs                      100%           -
     Gain/loss on property disposition                90%          10%
     Operating and administrative costs (2)           90%          10%
     Depreciation, depletion and amortization
      of oil and gas properties                      100%           -
     All other costs                                  90%          10%

          (1)All  organization  costs in excess of 3%  of  initial  capital
          contributions  will be paid by the Managing General  Partner  and
          will  be treated as a capital contribution.  The Partnership paid
          the  Managing  General Partner an amount equal to 3%  of  initial
          capital contributions for such organization costs.

          (2)Administrative costs in any year which exceed  2%  of  capital
          contributions shall be paid by the Managing General  Partner  and
          will be treated as a capital contribution.

2.   Summary of Significant Accounting Policies
     The  interim financial information as of March 31, 2001, and  for  the
     three  months ended March 31, 2001, is unaudited.  Certain information
     and  footnote  disclosures normally included in  financial  statements
     prepared  in accordance with generally accepted accounting  principles
     have been condensed or omitted in this Form 10-Q pursuant to the rules
     and  regulations of the Securities and Exchange Commission.   However,
     in  the  opinion  of  management, these interim  financial  statements
     include all the necessary adjustments to fairly present the results of
     the interim periods and all such adjustments are of a normal recurring
     nature.  The interim consolidated financial statements should be  read
     in  conjunction  with the audited financial statements  for  the  year
     ended December 31, 2000.


Item 2.   Management's  Discussion and Analysis of Financial Condition  and
          Results of Operations

General

Southwest Royalties Institutional Income Fund X-B, L.P. was organized as  a
Delaware  limited  partnership on November 27, 1990. The offering  of  such
limited  partnership interests began December 1, 1990 as part  of  a  shelf
offering registered under the name Southwest Royalties Institutional  1990-
91  Income Program.  Minimum capital requirements for the Partnership  were
met  on  March 11, 1991, with the offering of limited partnership interests
concluding September 30, 1991, with total limited partner contributions  of
$5,590,500.

The Partnership was formed to acquire royalty and net profits interests  in
producing  oil  and  gas properties, to produce and market  crude  oil  and
natural  gas  produced  from such properties, and  to  distribute  the  net
proceeds from operations to the limited and general partners.  Net revenues
from  producing  oil  and gas properties will not be  reinvested  in  other
revenue  producing  assets except to the extent that production  facilities
and wells are improved or reworked or where methods are employed to improve
or enable more efficient recovery of oil and gas reserves.

Increases   or   decreases   in  Partnership   revenues   and,   therefore,
distributions  to partners will depend primarily on changes in  the  prices
received  for  production,  changes in volumes of  production  sold,  lease
operating  expenses, enhanced recovery projects, offset drilling activities
pursuant  to farm-out arrangements, sales of properties, and the  depletion
of  wells.   Since  wells deplete over time, production  can  generally  be
expected to decline from year to year.

Well  operating costs and general and administrative costs usually decrease
with   production   declines;  however,  these  costs  may   not   decrease
proportionately.  Net income available for distribution to the partners  is
therefore expected to fluctuate in later years based on these factors.

Based on current conditions, management anticipates performing no workovers
during  2001 or 2002 to enhance production.  Workovers may be performed  in
the  years  2003  and  2004.   The partnership  may  have  an  increase  in
production volumes the year 2003 and 2004, otherwise, the partnership  will
most  likely  experience the historical production decline of approximately
7% per year.

Oil and Gas Properties

Oil  and  gas  properties  are accounted for at cost  under  the  full-cost
method.  Under this method, all productive and nonproductive costs incurred
in  connection with the acquisition, exploration and development of oil and
gas  reserves  are capitalized.  Gain or loss on the sale of  oil  and  gas
properties  is not recognized unless significant oil and gas  reserves  are
involved.

The  Partnership's policy for depreciation, depletion and  amortization  of
oil  and  gas  properties is computed under the units  of  revenue  method.
Under the units of revenue method, depreciation, depletion and amortization
is  computed  on  the  basis of current gross revenues from  production  in
relation  to future gross revenues, based on current prices, from estimated
production of proved oil and gas reserves.

Should the net capitalized costs exceed the estimated present value of  oil
and gas reserves, discounted at 10%, such excess costs would be charged  to
current  expense.  As of March 31, 2001, the net capitalized costs did  not
exceed the estimated present value of oil and gas reserves.


Results of Operations

A.  General Comparison of the Quarters Ended March 31, 2001 and 2000

The  following  table  provides certain information  regarding  performance
factors for the quarters ended March 31, 2001 and 2000:

                                               Three Months
                                                  Ended         Percentage
                                                         March          31,
Increase
                                              2001      2000    (Decrease)
                                              ----      ----    ----------
Average price per barrel of oil           $   26.69     25.37       5%
Average price per mcf of gas              $    5.96      2.91     105%
Oil production in barrels                     5,500     5,300       4%
Gas production in mcf                        17,000    16,300       4%
Income from net profits interests         $ 146,261    50,269     191%
Partnership distributions                 $ 125,000    55,000     127%
Limited partner distributions             $ 112,500    49,500     127%
Per unit distribution to limited
 partners                                 $   10.06      4.43     127%
Number of limited partner units              11,181    11,181

Revenues

The  Partnership's income from net profits interests increased to  $146,261
from  $50,269 for the quarters ended March 31, 2001 and 2000, respectively,
an increase of 191%.  The principal factors affecting the comparison of the
quarters ended March 31, 2001 and 2000 are as follows:

1.  The  average  price  for a barrel of oil received  by  the  Partnership
    increased  during the quarter ended March 31, 2001 as compared  to  the
    quarter  ended March 31, 2000 by 5%, or $1.32 per barrel, resulting  in
    an  increase  of  approximately  $7,300  in  income  from  net  profits
    interests.  Oil sales represented 59% of total oil and gas sales during
    the  quarter ended March 31, 2001 as compared to 74% during the quarter
    ended March 31, 2000.

    The  average  price  for  an  mcf of gas received  by  the  Partnership
    increased  during the same period by 105%, or $3.05 per mcf,  resulting
    in  an  increase  of approximately $51,900 in income from  net  profits
    interests.

    The  total  increase in income from net profits interests  due  to  the
    change  in prices received from oil and gas production is approximately
    $59,200.   The market price for oil and gas has been extremely volatile
    over  the  past  decade, and management expects  a  certain  amount  of
    volatility to continue in the foreseeable future.


2.  Oil  production increased approximately 200 barrels or  4%  during  the
    quarter ended March 31, 2001 as compared to the quarter ended March 31,
    2000,  resulting in an increase of approximately $5,100 in income  from
    net profits interests.

    Gas  production increased approximately 700 mcf or 4% during  the  same
    period, resulting in an increase of approximately $2,000 in income from
    net profits interests.

    The  total  increase in income from net profits interests  due  to  the
    change in production is approximately $7,100.

3.  Lease  operating  costs  and  production  taxes  were  23%  lower,   or
    approximately $29,600 less during the quarter ended March 31,  2001  as
    compared  to  the  quarter  ended March  31,  2000.   The  decrease  in
    primarily  the result of repairs and maintenance performed  during  the
    first quarter of 2000.

Costs and Expenses

Total costs and expenses increased to $29,157 from $27,251 for the quarters
ended  March  31,  2001 and 2000, respectively, an  increase  of  7%.   The
increase is the result of higher depletion expense, partially offset  by  a
decrease in general and administrative expense.

1.  General and administrative costs consists of independent accounting and
    engineering  fees,  computer services, postage,  and  Managing  General
    Partner  personnel costs.  General and administrative  costs  decreased
    less  than 1% or approximately $100 during the quarter ended March  31,
    2001 as compared to the quarter ended March 31, 2000.

2.  Depletion expense increased to $10,000 for the quarter ended March  31,
    2001  from  $8,000  for the same period in 2000.   This  represents  an
    increase  of 25%.  Depletion is calculated using the units  of  revenue
    method  of  amortization based on a percentage of current period  gross
    revenues  to  total future gross oil and gas revenues, as estimated  by
    the  Partnership's  independent  petroleum  consultants.   Contributing
    factors  to  the increase in depletion expense between the  comparative
    periods  were an increase in the price of oil and gas used to determine
    the Partnership's reserves, and the increase in oil and gas sales.


Liquidity and Capital Resources

The  primary source of cash is from operations, the receipt of income  from
interests in oil and gas properties.  The Partnership knows of no  material
change, nor does it anticipate any such change.

Cash flows provided by operating activities were approximately $129,200  in
the  quarter ended March 31, 2001 as compared to approximately  $58,300  in
the quarter ended March 31, 2000.  The primary source of the 2001 cash flow
from operating activities was profitable operations.

Cash flows used in financing activities were approximately $125,000 in  the
quarter  ended March 31, 2001 as compared to approximately $55,000  in  the
quarter ended March 31, 2000.  The only use in financing activities was the
distributions to partners.

Total  distributions during the quarter ended March 31, 2001 were  $125,000
of  which  $112,500 was distributed to the limited partners and $12,500  to
the general partners.  The per unit distribution to limited partners during
the  quarter  ended March 31, 2001 was $10.06.  Total distributions  during
the  quarter  ended  March  31,  2000 were $55,000  of  which  $49,500  was
distributed  to  the limited partners and $5,500 to the  general  partners.
The  per  unit  distribution to limited partners during the  quarter  ended
March 31, 2000 was $4.43.

The  source  for  the  2001  distributions of $125,000  were  oil  and  gas
operations  of  approximately  $129,200,  resulting  in  excess  cash   for
contingencies or subsequent distributions to partners.  The sources for the
2000  distributions of $55,000 were oil and gas operations of approximately
$58,300,   resulting  in  excess  cash  for  contingencies  or   subsequent
distributions to partners.

Since  inception of the Partnership, cumulative monthly cash  distributions
of  $5,222,302  have  been made to the partners.  As  of  March  31,  2001,
$4,759,115 or $425.64, per limited partner unit has been distributed to the
limited partners, representing a 85% return of the capital contributed.

As of March 31, 2001, the Partnership had approximately $201,200 in working
capital.   The  Managing  General Partner knows of no  unusual  contractual
commitments  and  believes  the  revenues  generated  from  operations  are
adequate to meet the needs of the Partnership.

Item 3.   Quantitative and Qualitative Disclosures About Market Risk

The  Partnership  is  not a party to any derivative or embedded  derivative
instruments.


                       PART II. - OTHER INFORMATION


Item 1.   Legal Proceedings

          None

Item 2.   Changes in Securities

          None

Item 3.   Defaults Upon Senior Securities

          None

Item 4.   Submission of Matter to a Vote of Security Holders

          None

Item 5.   Other Information

          None

Item 6.   Exhibits and Reports on Form 8-K

               (c)  Reports on Form 8-K:

                     No  reports on Form 8-K were filed during the  quarter
               for which this report is filed.


                                SIGNATURES


Pursuant  to the requirements of the Securities Exchange Act of  1934,  the
registrant  has duly caused this report to be signed on its behalf  by  the
undersigned thereunto duly authorized.


                              SOUTHWEST ROYALTIES INSTITUTIONAL
                              INCOME FUND X-B, L.P.
                              a Delaware limited partnership


                              By:  Southwest Royalties, Inc.
                                   Managing General Partner


                              By:  /s/ Bill E. Coggin
                                   ------------------------------
                                   Bill E. Coggin, Vice President
                                   and Chief Financial Officer



Date:  May 15, 2001