22
                                 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 September 30, 2005

                                    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

          SOUTWEST 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.)

                               6 Desta Drive
                           Midland, Texas 79705
                 (Address of principal executive offices)

                               432-682-6324
                      (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 ___

Indicate  by check mark whether the registrant is an accelerated filer  (as
defined in Exchange Act Rule 12b-2).     Yes     No  X

The  registrant's  outstanding  securities  consist  of  Units  of  limited
partnership  interests for which there exists no established public  market
from which to base a calculation of aggregate market value.


         The total number of pages contained in this report is 22.



Glossary of Oil and Gas Terms
The  following are abbreviations and definitions of terms commonly used  in
the  oil  and  gas industry that are used in this filing.  All  volumes  of
natural gas referred to herein are stated at the legal pressure base to the
state  or area where the reserves exit and at 60 degrees Fahrenheit and  in
most instances are rounded to the nearest major multiple.

     Bbl. One stock tank barrel, or 42 United States gallons liquid volume.

     Developmental well. A well drilled within the proved area of an oil or
natural gas reservoir to the depth of a stratigraphic horizon known  to  be
productive.

     Exploratory well. A well drilled to find and produce oil or gas in  an
unproved  area to find a new reservoir in a field previously  found  to  be
productive of oil or natural gas in another reservoir or to extend a  known
reservoir.

     Farm-out  arrangement. An agreement whereby the owner of the leasehold
or  working  interest  agrees to assign his interest  in  certain  specific
acreage  to  the assignee, retaining some interest, such as  an  overriding
royalty interest, subject to the drilling of one (1) or more wells or other
performance by the assignee.

     Field. An area consisting of a single reservoir or multiple reservoirs
all  grouped  on  or  related to the same individual geological  structural
feature and/or stratigraphic condition.

     Mcf. One thousand cubic feet.

     Net  Profits  Interest.  An agreement whereby  the  owner  receives  a
specified  percentage of the defined net profits from a producing  property
in  exchange for consideration paid.  The net profits interest  owner  will
not otherwise participate in additional costs and expenses of the property.

     Oil. Crude oil, condensate and natural gas liquids.

     Overriding  royalty  interest. Interests that  are  carved  out  of  a
working  interest, and their duration is limited by the term of  the  lease
under which they are created.


     Present  value  and  PV-10 Value. When used with respect  to  oil  and
natural gas reserves, the estimated future net revenue to be generated from
the  production of proved reserves, determined in all material respects  in
accordance  with  the  rules and regulations of the  SEC  (generally  using
prices  and costs in effect as of the date indicated) without giving effect
to  non-property  related  expenses  such  as  general  and  administrative
expenses,  debt service and future income tax expenses or to  depreciation,
depletion  and  amortization, discounted using an annual discount  rate  of
10%.

     Production  costs.  Costs incurred to operate and maintain  wells  and
related  equipment  and facilities, including depreciation  and  applicable
operating  costs  of support equipment and facilities and  other  costs  of
operating and maintaining those wells and related equipment and facilities.

     Proved Area. The part of a property to which proved reserves have been
specifically attributed.

     Proved  developed oil and gas reserves. Proved developed oil  and  gas
reserves  are  reserves that can be expected to be recovered from  existing
wells with existing equipment and operating methods.

     Proved properties. Properties with proved reserves.

     Proved  reserves. The estimated quantities of crude oil, natural  gas,
and  natural  gas liquids that geological and engineering data  demonstrate
with  reasonable  certainty to be recoverable in future  years  from  known
reservoirs under existing economic and operating conditions.

     Proved  undeveloped reserves. Proved undeveloped oil and gas  reserves
are  reserves that are expected to be recovered from new wells on undrilled
acreage,  or  from existing wells where a relatively major  expenditure  is
required for recompletion.

     Reservoir.  A porous and permeable underground formation containing  a
natural  accumulation  of  producible  oil  or  gas  that  is  confined  by
impermeable  rock  or water barriers and is individual  and  separate  from
other reservoirs.

     Royalty  interest.  An  interest in an oil and  natural  gas  property
entitling  the  owner to a share of oil or natural gas production  free  of
costs of production.

     Working  interest.  The operating interest that gives  the  owner  the
right  to  drill, produce and conduct operating activities on the  property
and a share of production.

     Workover.  Operations  on  a producing well  to  restore  or  increase
production.



                      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, 2004, which are found in the Registrant's Form
10-K  Report  for  2004 filed with the Securities and Exchange  Commission.
The December 31, 2004 balance sheet included herein has been taken from the
Registrant's  2004 Form 10-K Report.  Operating results for the  three  and
nine-month  periods ended September 30, 2005 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

                                 Septembe  December
                                  r 30,      31,
                                   2005      2004
                                  -----     -----
                                 (unaudit
                                   ed)
Assets
- ---------

Current assets:
 Cash and cash equivalents    $  97,155    73,836
  Receivable  from  Managing     113,454   122,060
General Partner
   New   Mexico  withholding     8,421     -
prepayment
                                 --------  --------
                                 ----      ----
   Total current assets          219,030   195,896
                                 --------  --------
                                 ----      ----
Oil  and  gas  properties  -
using the full-
 cost method of accounting       3,933,60  3,933,60
                                 9         9
       Less      accumulated
depreciation,
         depletion       and     3,629,99  3,616,77
amortization                     7         1
                                 --------  --------
                                 ----      ----
      Net   oil   and    gas     303,612   316,838
properties
                                 --------  --------
                                 ----      ----
                              $  522,642   512,734
                                 =======   =======

Liabilities  and   Partners'
Equity
- ----------------------------
- ----

Current     liability      -  $  1,610     -
distribution payable
                                 --------  --------
                                 ----      ----

Asset retirement obligation      221,682   217,668
                                 --------  --------
                                 ----      ----
Partners' equity (deficit):
 General partners                (45,365)  (47,116)
 Limited partners                344,715   342,182
                                 --------  --------
                                 ----      ----
   Total partners' equity        299,350   295,066
                                 --------  --------
                                 ----      ----
                              $  522,642   512,734
                                 =======   =======













                  The accompanying notes are an integral
                    part of these financial statements.


          Southwest Royalties Institutional Income Fund X-B, L.P.
                         Statements of Operations
                                (unaudited)

                                    Three Months Ended   Nine Months Ended
                                      September 30,        September 30,
                                     2005       2004      2005      2004
                                     -----     -----      -----     -----
Revenues
- ------------
Income from net profits          $ 254,322   159,626    638,422   399,197
interests
Interest                           403       149        965       254
Other                              -         -          -         250
                                   --------  ---------  --------  --------
                                   --        -          --        --
                                   254,725   159,775    639,387   399,701
                                   --------  ---------  --------  --------
                                   --        -          --        --
Expenses
- ------------
Depreciation, depletion and        4,503     5,154      13,226    15,154
amortization
Accretion of asset retirement      2,367     4,107      7,097     12,339
obligation
General and administrative         20,418    22,429     64,780    68,166
                                   --------  ---------  --------  --------
                                   --        -          --        --
                                   27,288    31,690     85,103    95,659
                                   --------  ---------  --------  --------
                                   --        -          --        --
Net income                       $ 227,437   128,085    554,284   304,042
                                   ======    ======     ======    ======
Net income allocated to:

  Managing General Partner       $ 20,875    11,992     51,076    28,728
                                   ======    ======     ======    ======
  General Partner                $ 2,319     1,332      5,675     3,192
                                   ======    ======     ======    =====
  Limited Partners               $ 204,243   114,761    497,533   272,122
                                   ======    ======     ======    ======
     Per limited partner unit    $  18.27
                                             10.26      44.50     24.34
                                   ======    ======     ======    ======




















                  The accompanying notes are an integral
                    part of these financial statements.
<PAGE
          Southwest Royalties Institutional Income Fund X-B, L.P.
                         Statements of Cash Flows
                                (unaudited)

                                                     Nine Months Ended
                                                       September 30,
                                                       2005     2004
                                                      -----     -----
            Cash flows from operating activities

            Cash received from income from net
              profits interests                    $ 635,524  319,186
            Cash paid to suppliers                   (64,780  (68,166)
                                                     )
            Interest received                        965      254
            Other                                    -        250
                                                     -------  --------
                                                     ---      --
              Net cash provided by operating         571,709  251,524
            activities
                                                     -------  --------
                                                     ---      --
            Cash flows from financing activities

            Distributions to partners                (550,00  (168,110
                                                     0)       )
            Increase (decrease) in distribution      1,610    (332)
            payable
                                                     -------  --------
                                                     ---      --
              Net cash used in financing             (548,39  (168,442
            activities                               0)       )
                                                     -------  --------
                                                     ---      --

              Net increase in cash and cash          23,319   83,082
            equivalents

            Beginning of period                      73,836   11,800
                                                     -------  --------
                                                     ---      --
            End of period                          $ 97,155   94,882
                                                     ======   ======
            Reconciliation of net income to net
            cash
            provided by operating activities

            Net income                             $ 554,284  304,042

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

            Depreciation, depletion and              13,226   15,154
            amortization
            Accretion of asset retirement            7,097    12,339
            obligation
            Settlement of ARO for P&A wells          (3,083)  -
            Decrease (increase) in receivables       185      (80,011)
                                                     -------  --------
                                                     ---      --
            Net cash provided by operating         $ 571,709  251,524
            activities
                                                     ======   ======
            Noncash investing and financing
            activities:

            Increase in oil and gas properties -
            SFAS No. 143
              Add new wells                        $ -        57
                                                     ======   ======
            Decrease in oil and gas properties -
            SFAS No. 143
              Plug and abandoned wells             $ -        651
                                                     ======   ======

                  The accompanying notes are an integral
                    part of these financial statements.

         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.  a  wholly  owned  subsidiary of Clayton Williams  Energy,  Inc.,
     serves as the Managing General Partner and Blue Heel Company, a wholly
     owned  subsidiary of Southwest Royalties, Inc., acquired  the  general
     partner interest from H.H. Wommack, III.  Revenues, costs and expenses
     are allocated as follows:

                         Limited   General
                         Partners  Partners
                         --------  --------
Interest   income    on  100%      -
capital contributions
Oil and gas sales        90%       10%
All other revenues       90%       10%
Organization        and  100%      -
offering costs (1)
Amortization         of  100%      -
organization costs
Property    acquisition  100%      -
costs
Gain/loss  on  property  90%       10%
disposition
Operating           and  90%       10%
administrative    costs
(2)
Depreciation, depletion
and amortization
   of   oil   and   gas  100%      -
properties
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 September 30, 2005,  and  for
     the  three  and  nine months ended September 30, 2005,  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 Partnership's Annual
     Report on Form 10-K for the year ended December 31, 2004.

     In September 2004, the Securities and Exchange Commission issued Staff
     Accounting  Bulletin No. 106 ("SAB 106"). SAB 106  expresses  the  SEC
     staff's views regarding SFAS No. 143 and its impact on both the  full-
     cost  ceiling  test  and  the calculation of  depletion  expense.   In
     accordance  with  SAB  106, beginning in the first  quarter  of  2005,
     undiscounted abandonment costs for wells to be drilled in  the  future
     to develop proved reserves are included in the unamortized cost of oil
     and  gas  properties, net of related salvage value,  for  purposes  of
     computing  depreciation,  depletion  and  amortization  ("DD&A").  The
     implementation  of  SAB  106 did not have a  material  impact  on  our
     financial statements.


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.  The  economic
life  of  the  Partnership  thus  depends on  the  period  over  which  the
Partnership's oil and gas reserves are economically recoverable

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 farmout 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.

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
sold.

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 September 30, 2005, the net capitalized costs  did
not exceed the estimated present value of oil and gas reserves.



The  Partnership's  interest  in oil and gas  properties  consists  of  net
profits  interests  in  proved properties located  within  the  continental
United  States.   A net profits interest is created when  the  owner  of  a
working  interest in a property enters into an arrangement  providing  that
the  net profits interest owner will receive a stated percentage of the net
profit  from  the  property.   The  net profits  interest  owner  will  not
otherwise participate in additional costs and expenses of the property.

The  Partnership recognizes income from its net profits interest in oil and
gas property on an accrual basis, while the quarterly cash distributions of
the net profits interest are based on a calculation of actual cash received
from  oil  and  gas sales, net of expenses incurred during  that  quarterly
period.   If  the  net  profits interest calculation  results  in  expenses
incurred  exceeding the oil and gas income received during  a  quarter,  no
cash  distribution is due to the Partnership's net profits  interest  until
the  deficit is recovered from future net profits.  The Partnership accrues
a quarterly loss on its net profits interest provided there is a cumulative
net  amount  due for accrued revenue as of the balance sheet date.   As  of
September 30, 2005, there were no timing differences, which resulted  in  a
deficit net profit interest.

Critical Accounting Policies

The  Partnership follows the full cost method of accounting for its oil and
gas  properties.   The  full cost method subjects  companies  to  quarterly
calculations of a "ceiling", or limitation on the amount of properties that
can  be capitalized on the balance sheet.  If the Partnership's capitalized
costs  are in excess of the calculated ceiling, the excess must be  written
off as an expense.

The  Partnership's discounted present value of its proved oil  and  natural
gas  reserves  is  a  major  component  of  the  ceiling  calculation,  and
represents  the  component  that requires the  most  subjective  judgments.
Estimates  of  reserves are forecasts based on engineering data,  projected
future  rates  of  production and the timing of future  expenditures.   The
process  of  estimating oil and natural gas reserves  requires  substantial
judgment,  resulting  in  imprecise determinations,  particularly  for  new
discoveries.   Different reserve engineers may make different estimates  of
reserve quantities based on the same data.

The  passage  of  time  provides  more  qualitative  information  regarding
estimates of reserves, and revisions are made to prior estimates to reflect
updated  information.   However,  there  can  be  no  assurance  that  more
significant  revisions  will not be necessary in  the  future.   If  future
significant  revisions  are  necessary  that  reduce  previously  estimated
reserve quantities, it could result in a full cost property writedown.   In
addition to the impact of these estimates of proved reserves on calculation
of  the  ceiling,  estimates  of proved reserves  are  also  a  significant
component  of  the calculation of depletion, depreciation, and amortization
("DD&A").

While  the quantities of proved reserves require substantial judgment,  the
associated prices of oil and natural gas reserves that are included in  the
discounted  present  value of the reserves do not  require  judgment.   The
ceiling calculation dictates that prices and costs in effect as of the last
day  of  the  period are generally held constant indefinitely. Because  the
ceiling  calculation dictates that prices in effect as of the last  day  of
the  applicable quarter are held constant indefinitely, the resulting value
is  not indicative of the true fair value of the reserves.  Oil and natural
gas  prices have historically been cyclical and, on any particular  day  at
the  end of a quarter, can be either substantially higher or lower than the
Partnership's  long-term price forecast that is a barometer for  true  fair
value.



Results of Operations

General Comparison of the Quarters Ended September 30, 2005 and 2004

The  following  table  provides certain information  regarding  performance
factors for the quarters ended September 30, 2005 and 2004:

                                    Three Months
                                       Ended         Percenta
                                                        ge
                                   September 30,     Increase
                                   2005      2004    (Decreas
                                                        e)
                                  -----     -----    --------
                                                        --
Oil production in barrels        4,740     4,520     5%
Gas production in mcf            16,800    17,979    (7%)
Total BOE                        7,540     7,517     -
Average price per barrel  of  $   60.97              44%
oil                                        42.21
Average price per mcf of gas  $    7.54              46%
                                           5.15
Income   from  net   profits  $  254,322   159,626   59%
interests
Partnership distributions     $  175,000   100,000   75%
Limited              partner  $  157,500   90,000    75%
distributions
Per  unit  distribution   to  $   14.09              75%
limited partners                           8.05
Number  of  limited  partner     11,181    11,181
units

Income from net profits

The  Partnership's income from net profits interests increased to  $254,322
from  $159,626  for  the  quarters  ended  September  30,  2005  and  2004,
respectively,  an  increase of 59%.  The principal  factors  affecting  the
comparison  of  the  quarters ended September 30,  2005  and  2004  are  as
follows:

The average price for a barrel of oil received by the Partnership increased
during  the  quarter ended September 30, 2005 as compared  to  the  quarter
ended  September  30, 2004 by 44%, or $18.76 per barrel,  resulting  in  an
increase  of  approximately $88,900 in income from net  profits  interests.
Oil  sales  represented 70% of total oil and gas sales during  the  quarter
ended  September  30,  2005  as compared to 67% during  the  quarter  ended
September 30, 2004.

The  average price for an mcf of gas received by the Partnership  increased
during  the same period by 46%, or $2.39 per mcf, resulting in an  increase
of approximately $40,200 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 $129,100.
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.


Oil production increased approximately 220 barrels or 5% during the quarter
ended  September  30, 2005 as compared to the quarter ended  September  30,
2004,  resulting in an increase of approximately $9,300 in income from  net
profits interests.

Gas  production  decreased approximately 1,179 mcf or 7%  during  the  same
period, resulting in a decrease of approximately $6,100 in income from  net
profits interests.

The net increase in income from net profits interests due to the change  in
production is approximately $3,200.

Lease   operating  costs  and  production  taxes  were   30%   higher,   or
approximately $37,600 more during the quarter ended September 30,  2005  as
compared  to the quarter ended September 30, 2004.  The increase  in  lease
operating  costs is due to well repairs on one property.  Production  taxes
increased  from  the  higher revenues resulting from  higher  oil  and  gas
prices.

Costs and Expenses

Total costs and expenses decreased to $27,288 from $31,690 for the quarters
ended  September 30, 2005 and 2004, respectively, a decrease of  14%.   The
decrease is a result of lower accretion expense, general and administrative
expense and depletion expense.

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  9%   or
approximately  $2,000  during  the quarter  ended  September  30,  2005  as
compared to the quarter ended September 30, 2004.

Depletion  expense decreased to $4,503 for the quarter ended September  30,
2005  from $5,154 for the same period in 2004.  This represents a  decrease
of 13%.  The contributing factor to the decrease in depletion expense is in
relation  to  the  BOE depletion rate for the quarter ended  September  30,
2005,  which was $.60 applied to 7,540 BOE as compared to $.69  applied  to
7,517 BOE for the same period in 2004.  The lower depletion rate in 2005 is
due  to the upward revision in reserve estimates resulting from higher  oil
and gas prices.

Accretion  expense decreased to $2,367 for the quarter ended September  30,
2005  from $4,107 for the same period in 2004.  This represents a  decrease
of  42%.   The  decrease  in accretion is from discontinuing  accretion  on
several wells that reached their projected end of life in 2004.



B.   General Comparison of the Nine-Month Periods Ended September 30,  2005
and 2004

The  following  table  provides certain information  regarding  performance
factors for the nine-month periods ended September 30, 2005 and 2004:

                               Nine Months
                                  Ended         Percenta
                                                   ge
                              September 30,     Increase
                              2005      2004    (Decreas
                                                   e)
                             -----     -----    --------
                                                   --
Oil    production    in     14,162    13,820    2%
barrels
Gas production in mcf       49,666    48,459    2%
Total BOE                   22,440    21,897    2%
Average    price    per  $   53.50              43%
barrel of oil                         37.36
Average  price per  mcf  $    6.38              20%
of gas                                5.30
Income from net profits  $  638,422   399,197   60%
interests
Partnership              $  550,000   168,110   227%
distributions
Limited         partner  $  495,000   153,110   223%
distributions
Per  unit  distribution  $   44.27              223%
to limited partners                   13.69
Number    of    limited     11,181    11,181
partner units

Income from net profits

The  Partnership's income from net profits interests increased to  $638,422
from  $399,197  for  the nine months ended September  30,  2005  and  2004,
respectively,  an  increase of 60%.  The principal  factors  affecting  the
comparison  of  the nine months ended September 30, 2005 and  2004  are  as
follows:

The average price for a barrel of oil received by the Partnership increased
during  the  nine months ended September 30, 2005 as compared to  the  nine
months ended September 30, 2004 by 43%, or $16.14 per barrel, resulting  in
an increase of approximately $228,600 in income from net profits interests.
Oil sales represented 71% of total oil and gas sales during the nine months
ended September 30, 2005 and 67% during the nine months ended September 30,
2004.

The  average price for an mcf of gas received by the Partnership  increased
during  the same period by 20%, or $1.08 per mcf, resulting in an  increase
of approximately $53,600 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 $282,200.
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.


Oil  production increased approximately 342 barrels or 2% during  the  nine
months  ended  September  30, 2005 as compared to  the  nine  months  ended
September  30, 2004, resulting in an increase of approximately  $12,800  in
income from net profits interests.

Gas  production  increased approximately 1,207 mcf or 2%  during  the  same
period, resulting in an increase of approximately $6,400 in income from net
profits interests.

The  total increase in income from net profits interests due to the  change
in production is approximately $19,200.

Lease   operating  costs  and  production  taxes  were   17%   higher,   or
approximately $62,000 more during the nine months ended September 30,  2005
as  compared to the nine months ended September 30, 2004.  The increase  in
lease  operating costs is due to well repairs on one property.   Production
taxes  also increased due to the higher revenues resulting from higher  oil
and gas prices.

Costs and Expenses

Total  costs  and expenses decreased to $85,103 from $95,659 for  the  nine
months ended September 30, 2005 and 2004, respectively, a decrease of  11%.
The   decrease  is  a  result  of  lower  depletion  expense,  general  and
administrative expense and accretion expense.

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  5%   or
approximately  $3,400 during the nine months ended September  30,  2005  as
compared to the nine months ended September 30, 2004.

Depletion  expense decreased to $13,226 for the nine months ended September
30,  2005  from  $15,154 for the same period in 2004.   This  represents  a
decrease  of  13%.   The contributing factor to the decrease  in  depletion
expense is in relation to the BOE depletion rate for the nine months  ended
September  30,  2005, which was $.59 applied to 22,440 BOE as  compared  to
$.69  applied  to  21,897  BOE for the same  period  in  2004.   The  lower
depletion  rate in 2005 is due to the upward revision in reserve  estimates
resulting from higher oil and gas prices.

Accretion  expense decreased to $7,097 for the nine months ended  September
30,  2005  from  $12,339 for the same period in 2004.   This  represents  a
decrease of 42%.  The decrease in accretion is from discontinuing accretion
on several wells that reached their projected end of life in 2004.



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 $571,700  in
the  nine  months  ended  September 30, 2005 as compared  to  approximately
$251,500 in the nine months ended September 30, 2004.

Cash flows used in financing activities were approximately $548,400 in  the
nine  months ended September 30, 2005 as compared to approximately $168,400
in  the  nine  months ended September 30, 2004.  The only use in  financing
activities was the distributions to partners.

Total  distributions during the nine months ended September 30,  2005  were
$550,000  of  which  $495,000 was distributed to the limited  partners  and
$55,000  to  the  general partners.  The per unit distribution  to  limited
partners during the nine months ended September 30, 2005 was $44.27.  Total
distributions during the nine months ended September 30, 2004 were $168,110
of  which  $153,110 was distributed to the limited partners and $15,000  to
the general partners.  The per unit distribution to limited partners during
the nine months ended September 30, 2004 was $13.69.

The  source  for  the  2005  distributions of $550,000  were  oil  and  gas
operations  of  approximately  $571,700,  resulting  in  excess  cash   for
contingencies  or  subsequent  distributions.  The  source  for  the   2004
distributions  of  $168,110  were oil and gas operations  of  approximately
$251,500,   resulting  in  excess  cash  for  contingencies  or  subsequent
distributions.

Cumulative cash distributions of $6,768,023 have been made to the partners.
As  of  September 30, 2005, $6,151,112 or $550.14 per limited partner  unit
has  been  distributed  to  the  limited  partners,  representing  110%  of
contributed capital.

As  of  September 30, 2005, the Partnership had approximately  $217,400  in
working  capital.   The  Managing  General  Partner  knows  of  no  unusual
contractual  commitments.  The partnership held many long-lived  properties
at  inception,  however  due to the restrictions  on  property  development
imposed  by  the partnership agreement, the Partnership cannot develop  its
non-producing  properties.   Without continued development,  the  producing
reserves continue to deplete.  Accordingly, as the Partnership's properties
have  matured  and  depleted, the net cash flows from  operations  for  the
partnership  has  steadily  declined, except in  periods  of  substantially
increased  commodity pricing.  Maintenance of properties and administrative
expenses for the Partnership are increasing relative to production.  As the
properties   continue   to   deplete,   maintenance   of   properties   and
administrative costs as a percentage of production are expected to continue
to increase.



Recent Accounting Pronouncements

In  September  2004,  the Securities and Exchange Commission  issued  Staff
Accounting Bulletin No. 106 ("SAB 106"). SAB 106 expresses the SEC  staff's
views  regarding SFAS No. 143 and its impact on both the full-cost  ceiling
test and the calculation of depletion expense.  In accordance with SAB 106,
beginning in the first quarter of 2005, undiscounted abandonment costs  for
wells  to  be drilled in the future to develop proved reserves are included
in  the  unamortized cost of oil and gas properties, net of related salvage
value,  for  purposes of computing depreciation, depletion and amortization
("DD&A").  The implementation of SAB 106 did not have a material impact  on
our financial statements.



Item 3.   Quantitative and Qualitative Disclosures About Market Risk

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

Item 4.   Controls and Procedures

The  Managing  General  Partner  has established  disclosure  controls  and
procedures   that  are  adequate  to  provide  reasonable  assurance   that
management will be able to collect, process and disclose both financial and
non-financial information, on a timely basis, in the Partnership's  reports
to  the  SEC.   Disclosure controls and procedures  include  all  processes
necessary  to  ensure  that material information  is  recorded,  processed,
summarized  and  reported within the time periods specified  in  the  SEC's
rules  and  forms,  and  is  accumulated and  communicated  to  management,
including our chief executive and chief financial officers, to allow timely
decisions regarding required disclosures.

     With respect to these disclosure controls and procedures:

          management  has  evaluated the effectiveness  of  the  disclosure
          controls  and procedures as of the end of the period  covered  by
          this report;

          this evaluation was conducted under the supervision and with  the
          participation  of management, including the chief  executive  and
          chief financial officers of the Managing General Partner; and

          it  is  the  conclusion of chief executive  and  chief  financial
          officers  of  the Managing General Partner that these  disclosure
          controls   and   procedures  are  effective  in   ensuring   that
          information  that is required to be disclosed by the  Partnership
          in   reports  filed  or  submitted  with  the  SEC  is  recorded,
          processed,  summarized  and  reported  within  the  time  periods
          specified in the rules and forms established by the SEC.

Internal Control Over Financial Reporting
There  has  not been any change in the Partnership's internal control  over
financial  reporting that occurred during the quarter ended  September  30,
2005  that  has materially affected, or is reasonably likely to  materially
affect, its internal control over financial reporting.




                        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

          (a)  Exhibits:

               31.1 Rule 13a-14(a)/15d-14(a) Certification
               31.2 Rule 13a-14(a)/15d-14(a) Certification
               32.1 Certification of Chief Executive Officer
and Chief Financial Officer
                 Pursuant to 18 U.S.C. Section 1350, as adopted
                  Pursuant to Section 906 of the Sarbanes-Oxley Act of 2002





                                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/ L. Paul Latham
                                 L. Paul Latham
                                 President and Chief Executive Officer




Date:  November 14, 2005




                   SECTION 302 CERTIFICATION                Exhibit 31.1


I, L. Paul Latham, certify that:

1.   I  have  reviewed  this quarterly report on  Form  10-Q  of  Southwest
Royalties Institutional Income Fund X-B, L.P.

2.Based  on my knowledge, this report does not contain any untrue statement
  of  a  material fact or omit to state a material fact necessary  to  make
  the  statements  made,  in light of the circumstances  under  which  such
  statements  were made, not misleading with respect to the period  covered
  by this report;

3.Based  on  my  knowledge, the financial statements, and  other  financial
  information  included  in  this report, fairly present  in  all  material
  respects  the financial condition, results of operations and  cash  flows
  of the registrant as of, and for, the periods presented in this report;

4.The  registrant's other certifying officer(s) and I are  responsible  for
  establishing  and  maintaining disclosure  controls  and  procedures  (as
  defined   in  Exchange  Act  Rules  13a-15(e)  and  15d-15(e))  for   the
  registrant and have:

  a)Designed  such  disclosure  controls and  procedures,  or  caused  such
     disclosure   controls  and  procedures  to  be  designed   under   our
     supervision,  to  ensure  that material information  relating  to  the
     registrant, including its consolidated subsidiaries, is made known  to
     us  by others within those entities, particularly during the period in
     which this report is being prepared;

  b)Evaluated  the  effectiveness of the registrant's  disclosure  controls
     and  procedures and presented in this report our conclusions about the
     effectiveness of the disclosure controls and procedures, as of the end
     of the period covered by this report based on such evaluation; and

  c)Disclosed  in  this  report  any change in  the  registrant's  internal
     control over financial reporting that occurred during the registrant's
     most recent fiscal quarter (the registrant's fourth fiscal quarter  in
     the  case  of  an annual report) that has materially affected,  or  is
     reasonably  likely  to  materially affect, the  registrant's  internal
     control over financial reporting; and

5.The  registrant's other certifying officer(s) and I have disclosed, based
  on  our  most  recent  evaluation  of  internal  control  over  financial
  reporting,  to  the  registrant's auditors and  the  audit  committee  of
  registrant's  board  of directors (or persons performing  the  equivalent
  functions):

  a)All  significant deficiencies and material weaknesses in the design  or
     operation   of   internal  control  over  financial  reporting   which
     reasonably  likely  to  adversely affect the registrant's  ability  to
     record, process, summarize and report financial information; and

  b)Any  fraud, whether or not material, that involves management or  other
     employees  who  have  a significant role in the registrant's  internal
     control over financial reporting.


Date:  November 14, 2005           /s/ L. Paul Latham
                                   L. Paul Latham
                                   President and Chief Executive Officer
                                   of Southwest Royalties, Inc., the
                                   Managing General Partner of
                                   Southwest Royalties Institutional Income
Fund X-B, L.P.






                   SECTION 302 CERTIFICATION                Exhibit 31.2


I, Mel G. Riggs, certify that:

1.   I  have  reviewed  this quarterly report on  Form  10-Q  of  Southwest
Royalties Institutional Income Fund X-B, L.P.

2.Based  on my knowledge, this report does not contain any untrue statement
  of  a  material fact or omit to state a material fact necessary  to  make
  the  statements  made,  in light of the circumstances  under  which  such
  statements  were made, not misleading with respect to the period  covered
  by this report;

3.Based  on  my  knowledge, the financial statements, and  other  financial
  information  included  in  this report, fairly present  in  all  material
  respects  the financial condition, results of operations and  cash  flows
  of the registrant as of, and for, the periods presented in this report;

4.The  registrant's other certifying officer(s) and I are  responsible  for
  establishing  and  maintaining disclosure  controls  and  procedures  (as
  defined   in  Exchange  Act  Rules  13a-15(e)  and  15d-15(e))  for   the
  registrant and have:

  a)Designed  such  disclosure  controls and  procedures,  or  caused  such
     disclosure   controls  and  procedures  to  be  designed   under   our
     supervision,  to  ensure  that material information  relating  to  the
     registrant, including its consolidated subsidiaries, is made known  to
     us  by others within those entities, particularly during the period in
     which this report is being prepared;

  b)Evaluated  the  effectiveness of the registrant's  disclosure  controls
     and  procedures and presented in this report our conclusions about the
     effectiveness of the disclosure controls and procedures, as of the end
     of the period covered by this report based on such evaluation; and

  c)Disclosed  in  this  report  any change in  the  registrant's  internal
     control over financial reporting that occurred during the registrant's
     most recent fiscal quarter (the registrant's fourth fiscal quarter  in
     the  case  of  an annual report) that has materially affected,  or  is
     reasonably  likely  to  materially affect, the  registrant's  internal
     control over financial reporting; and

5.The  registrant's other certifying officer(s) and I have disclosed, based
  on  our  most  recent  evaluation  of  internal  control  over  financial
  reporting,  to  the  registrant's auditors and  the  audit  committee  of
  registrant's  board  of directors (or persons performing  the  equivalent
  functions):

  a)All  significant deficiencies and material weaknesses in the design  or
     operation   of   internal  control  over  financial  reporting   which
     reasonably  likely  to  adversely affect the registrant's  ability  to
     record, process, summarize and report financial information; and

  b)Any  fraud, whether or not material, that involves management or  other
     employees  who  have  a significant role in the registrant's  internal
     control over financial reporting.


Date:  November 14, 2005           /s/ Mel G. Riggs
                                   Mel G. Riggs
                                     Vice  President  and  Chief  Financial
Officer of
                                   Southwest Royalties, Inc., the
                                   Managing General Partner of
                                   Southwest Royalties Institutional Income
Fund X-B, L.P.







                                                               Exhibit 32.1

               CERTIFICATION OF CHIEF EXECUTIVE OFFICER AND
                          CHIEF FINANCIAL OFFICER

Pursuant to 18 U.S.C.  1350 and in connection with the accompanying  report
on  Form  10-Q for the period ended September 30, 2005 that is being  filed
concurrently with the Securities and Exchange Commission on the date hereof
(the  "Report"),  each of the undersigned officers of  Southwest  Royalties
Institutional Income Fund X-B, L.P. (the "Company"), hereby certifies that:

     1.    The Report fully complies with the requirements of section 13(a)
     or 15(d) of the Securities Exchange Act of 1934; and

     2.   The  information contained in the Report fairly presents, in  all
          material  respects,  the  financial  condition  and  results   of
          operation of the Company.


                                   /s/ L. Paul Latham
                                   L. Paul Latham
                                   President and Chief Executive Officer
                                        of Southwest Royalties, Inc., the
                                        Managing General Partner of
                                         Southwest  Royalties Institutional
                                   Income Fund X-B, L.P.

                                   November 14, 2005


                                   /s/ Mel G. Riggs
                                   Mel G. Riggs
                                   Vice   President  and  Chief   Financial
                                   Officer of
                                        Southwest Royalties, Inc., the
                                        Managing General Partner of
                                         Southwest  Royalties Institutional
                                   Income Fund X-B, L.P.

                                   November 14, 2005