----

|   | Exhibit      21 |
|--------|-----------------|

|   | SUBSIDIARIES      OF THE REGISTRANT |
|--------|-------------------------------------|

| ·   | Warrior      Gas Co., a Texas corporation, which has a wholly owned subsidiary, Clajon      Industrial Gas, Inc., a Texascorporation |
|--------------------|--------------------------------------------------------------------------------------------------------------------------------------|

| ·   | Clayton      Williams Trading Company, a Texascorporation |
|--------------------|-----------------------------------------------------------|

| ·   | Clayton      Williams Venezuela, Inc., a Delawarecorporation |
|--------------------|--------------------------------------------------------------|

| ·   | CWEI      Acquisitions, Inc., a Delawarecorporation |
|--------------------|-----------------------------------------------------|

| ·   | Clayton      Williams Pipeline Corporation (formerly Clayton Williams Midland, Inc.), a      Delaware corporation |
|--------------------|-------------------------------------------------------------------------------------------------------------------|

| ·   | CWEI      Romere Pass Acquisition Corp., a Delaware corporation, which is the sole      member of Romere Pass Acquisition, L.L.C. (formerly Romere Pass      Acquisition Corp.) |
|--------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

| ·   | Warrior      Mississippi Corporation, a Delawarecorporation |
|--------------------|-------------------------------------------------------------|

| ·   | Southwest      Royalties, Inc., a Delaware corporation, which has two wholly owned      subsidiaries, Blue Hill Company, a Delaware corporation and Tex-Hal      Partners, Inc., a Delawarecorporation |
|--------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

| ·   | CWEI      Longfellow Ranch I, L.P., a Texas limited  partnership |
|--------------------|------------------------------------------------------------------|

| ·   | CWEI      South Louisiana II, L.P., a Texas limited  partnership |
|--------------------|------------------------------------------------------------------|

| ·   | Rocky      Arroyo, L.P., a Texas limitedpartnership |
|--------------------|-----------------------------------------------------|

| ·   | CWEI      West Pyle/McGonagill, L.P., a Texas limited  partnership |
|--------------------|--------------------------------------------------------------------|

| ·   | CWEI      South Louisiana III, L.P., a Texas limited  partnership |
|--------------------|-------------------------------------------------------------------|

| ·   | CWEI      North Louisiana, L.P., a Texas limited  partnership |
|--------------------|---------------------------------------------------------------|

| ·   | Floyd      Prospect, L.P., a Texas limitedpartnership |
|--------------------|-------------------------------------------------------|

| ·   | Southwest      Royalties, Inc. Income Fund V, a Tennessee limited      partnership |
|--------------------|-----------------------------------------------------------------------------------------|

| ·   | Southwest      Royalties, Inc. Income Fund VI, a Tennessee limited      partnership |
|--------------------|------------------------------------------------------------------------------------------|

| ·   | Southwest      Oil and Gas Income Fund VII-A, L.P., a Delaware limited      partnership |
|--------------------|-----------------------------------------------------------------------------------------|

| ·   | Southwest      Royalties Institutional Income Fund VII-B, L.P., a Delaware limited      partnership |
|--------------------|-----------------------------------------------------------------------------------------------------|

| ·   | Southwest      Royalties, Inc. Income/Drilling Program 1987-I, L.P., a Delaware      limited partnership |
|--------------------|---------------------------------------------------------------------------------------------------------------|

| ·   | Southwest      Oil and Gas Income Fund VIII-A, L.P., a Delaware limited      partnership |
|--------------------|------------------------------------------------------------------------------------------|

| ·   | Southwest      Royalties Institutional Income Fund VIII-B, L.P., a Delaware limited      partnership |
|--------------------|------------------------------------------------------------------------------------------------------|

| ·   | Southwest      Combination Income/Drilling Program 1988, L.P., a Delaware limited      partnership |
|--------------------|----------------------------------------------------------------------------------------------------|

| ·   | Southwest      Oil and Gas Income Fund IX-A, L.P., a Delaware limited      partnership |
|--------------------|----------------------------------------------------------------------------------------|

| ·   | Southwest      Royalties Institutional Income Fund IX-B, L.P., a Delaware limited      partnership |
|--------------------|----------------------------------------------------------------------------------------------------|

| ·   | Southwest      Oil & Gas Income Fund X-A, L.P., a Delaware limited      partnership |
|--------------------|----------------------------------------------------------------------------------------------|

| ·   | Southwest      Royalties Institutional Income Fund X-A, L.P., a Delaware limited      partnership |
|--------------------|---------------------------------------------------------------------------------------------------|

| ·   | Southwest      Oil & Gas Income Fund X-B, L.P., a Delaware limited      partnership |
|--------------------|----------------------------------------------------------------------------------------------|

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

| ·   | Southwest      Oil & Gas Income Fund X-C, L.P., a Delaware limited      partnership |
|--------------------|----------------------------------------------------------------------------------------------|

----

|   | SUBSIDIARIES      OF THE REGISTRANT |
|--------|-------------------------------------|

|   | (Continued) |
|--------|-------------|

| ·   | Southwest      Royalties Institutional Income Fund X-C, L.P., a Delaware limited      partnership |
|--------------------|---------------------------------------------------------------------------------------------------|

| ·   | Southwest      Oil & Gas Income Fund XI-A, L.P., a Delaware limited      partnership |
|--------------------|-----------------------------------------------------------------------------------------------|

| ·   | Southwest      Institutional Income Fund XI-A, L.P., a Delaware limited      partnership |
|--------------------|------------------------------------------------------------------------------------------|

| ·   | Southwest      Developmental Drilling Fund 1990, L.P., a Delaware limited      partnership |
|--------------------|--------------------------------------------------------------------------------------------|

| ·   | Southwest      Developmental Drilling Fund 91-A, L.P., a Delaware limited      partnership |
|--------------------|--------------------------------------------------------------------------------------------|

| ·   | Southwest      Developmental Drilling Fund 92-A, L.P., a Delaware limited      partnership |
|--------------------|--------------------------------------------------------------------------------------------|

| ·   | Southwest      Developmental Drilling Fund 1993, L.P., a Delaware limited      partnership |
|--------------------|--------------------------------------------------------------------------------------------|

| ·   | Southwest      Royalties Institutional Income Fund XI-B, L.P., a Delaware limited      partnership |
|--------------------|----------------------------------------------------------------------------------------------------|

| ·   | Southwest      Developmental Drilling Fund 1994, L.P., a Delaware limited      partnership |
|--------------------|--------------------------------------------------------------------------------------------|

| ·   | Floyd      Prospect II, L.P., a Texas limitedpartnership |
|--------------------|----------------------------------------------------------|

| ·   | West      Coast Energy Properties GP, LLC, a Texas limited liability      company |
|--------------------|-----------------------------------------------------------------------------------|

| ·   | West      Coast Energy Properties, L.P., a Texas limited  partnership |
|--------------------|-----------------------------------------------------------------------|