CLAYTON WILLIAMS ENERGY, INC.
(Exact name of registrant as specified in its charter)

Copies to: William R. Volk Barry Burgdorf Vinson & Elkins L.L.P. The Terrace 7 2801 Via Fortuna, Suite 100 Austin, Texas 78746-7568 (512) 542-8400 (512) 542-8612 (Fax)

Approximate date of commencement of proposed sale to the public: From time to time after this Registration Statement becomes effective.

If the only securities being registered on this Form are being offered pursuant to dividend or interest reinvestment plans, please check the following box. o

If any of the securities being registered on this Form are being offered on a delayed or continuous basis pursuant to Rule 415 under the Securities Act of 1933, as amended (the "Securities Act"), other than securities offered only in connection with dividend or interest reinvestment plans, please check the following box. ý

If this Form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, please check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. o

If this Form is a post-effective amendment filed pursuant to Rule 462(c) under the Securities Act, please check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. o

If delivery of the prospectus is expected to be made pursuant to Rule 434, please check the following box. o

The registrant hereby amends this Registration Statement on such date or dates as may be necessary to delay its effective date until the registrant shall file a further amendment which specifically states that this Registration Statement shall thereafter become effective in accordance with Section 8(a) of the Securities Act of 1933 or until the Registration Statement shall become effective on such date as the Securities and Exchange Commission, acting pursuant to said Section 8(a), may determine.

The information in this preliminary prospectus is not complete and may be changed. The selling stockholders may not sell these securities until the registration statement filed with the Securities and Exchange Commission is effective. This prospectus is not an offer to sell these securities and it is not a solicitation of an offer to buy these securities in any state where the offer or sale is not permitted.

This prospectus relates to the offer and sale from time to time of up to 1,380,869 shares of our common stock by certain of our stockholders named in this prospectus. These stockholders acquired the shares directly from us in a private placement completed on May 25, 2004. We will not receive any proceeds from the sale of these shares although we are obligated to pay the expenses of preparing this prospectus and the related registration statement.

These shares are being registered to permit the selling stockholders to sell the shares from time to time in the public market. The selling stockholders may sell these shares through ordinary brokerage transactions, directly to market makers or through any other means described in "Plan of Distribution."

Our common stock is quoted on the Nasdaq National Market under the symbol "CWEI." On June 23, 2004, the last reported sale price of our common stock was $25.32 per share. The shares may be sold at market prices prevailing at the time of sale or at negotiated prices.

Investing in our Common Stock Involves Risks. See "Risk Factors" beginning on page 2.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved these securities or determined if this prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

Our principal executive offices are located at 6 Desta Drive, Suite 6500, Midland, Texas 79705-5510, and our telephone number at this location is (432) 682-6324.

You should rely only on the information contained or incorporated by reference in this prospectus. We have not authorized anyone to provide you with information that is different. This prospectus may only be used where it is legal to sell these securities. The information in this prospectus may only be accurate as of the date on the cover of this prospectus.

The information in this prospectus, including information and documents incorporated by reference, includes "forward-looking" statements within the meaning of Section 27A of the Securities Act of 1933 and Section 21E of the Securities Exchange Act of 1934. In general, all statements other than statements of historical fact are forward-looking statements. These forward-looking statements are based on management's current belief, based on currently available information, as to the outcome and timing of future events. However, management's assumptions and our future performance are subject to a wide range of business risks and uncertainties and we cannot assure you that these goals and projections can or will be met. Any number of factors could cause actual results to differ materially from those in the forward-looking statements, including, but not limited to:

All such forward-looking statements in this document are expressly qualified in their entirety by the cautionary statements in this paragraph, and we undertake no obligation to update or revise any forward-looking statements.

On May 21, 2004, we acquired through a merger all the outstanding common stock of Southwest Royalties, Inc. ("Southwest"), a privately held company engaged in oil and gas exploration, production, development and acquisition activities in the United States. In connection with the acquisition, we paid $57.1 million, or $45.01 per share, to holders of Southwest common stock and common stock warrants, assumed and refinanced approximately $113.9 million of Southwest's bank debt and incurred $13.3 million of merger-related costs and bank fees.

Southwest is now our wholly owned subsidiary. Substantially all of Southwest's properties are located in the Permian Basin area of Texas and southeastern New Mexico. Southwest owns interests in over 6,000 oil and gas wells, and is the operator of approximately 1,400 of these wells. We estimate that the Southwest acquisition added approximately 180 Bcfe to our proved oil and gas reserves as of the date of acquisition. Southwest reported proved reserves of 186 Bcfe as of December 31, 2003.

We have identified up to 200 gross (100 net) proved undeveloped well locations on leasehold acreage acquired through the Southwest transaction. We believe that pursuing developmental activities at these locations will complement our efforts to obtain oil and gas reserves through higher-risk exploration activities. We plan to increase spending on exploration and development activities during 2004 to approximately $94 million, excluding the cost of acquiring Southwest. Of these planned expenditures, approximately 78% will be on exploratory prospects. We expect expenditures to be more balanced between exploration and development activities in 2005. We may also decide to selectively divest properties acquired through the Southwest acquisition that are outside of our strategic focus.

We will account for the acquisition using the purchase method of accounting for business combinations. Under this method of accounting, we are deemed to be the acquirer, and Southwest's assets and liabilities will be revalued and recorded at their estimated fair values.

We funded the acquisition of Southwest with the proceeds of borrowings under a new bank credit facility arranged by Bank One, NA, consisting of a three-year, $300 million revolving credit facility and a four-year, $75 million senior term credit facility. The bank credit facility provides an initial borrowing base of $180 million, and replaced our previous credit facility, which had a borrowing base of $95 million. We borrowed $109.4 million under the revolving credit facility and $75 million under the term credit facility to finance the Southwest acquisition, and we borrowed $51.4 million under the revolving credit facility to refinance the outstanding balance under our previous credit facility.

On May 25, 2004, we sold 1,380,869 shares of our common stock in a private placement to the stockholders named in this prospectus at a price of $23.00 per share. We applied $25 million of the net proceeds from the private placement to reduce the outstanding balance under the senior term credit facility to $50 million and applied the remaining net proceeds of approximately $4.9 million to repay indebtedness under the revolving credit facility.

After giving effect to these transactions, our long-term debt (including current maturities) on a pro forma basis at March 31, 2004 increased from $55.6 million to $219 million and our stockholders' equity increased from $105.8 million to $135.7 million. As a result, our ratio of long-term debt to total capitalization increased from 34% to 62%. The loan agreements under our credit facility contain financial covenants that require us to maintain a current ratio of at least 1-to-1, a ratio of indebtedness to cash flow of not more than 3-to-1, and a ratio of reserve value to indebtedness of not less than 1.5-to-1. We are in compliance with these and other covenants under these agreements as of the date of this prospectus.

Our attempts to complete the State Lease 17378 #1 ("Fleur #1") well in Plaquemines Parish, Louisiana in intervals below 16,000 feet were unsuccessful. We successfully completed the Fleur #1 in a middle Miocene sand in intervals between 14,326 feet and 14,344 feet as an oil well and tested at an average 307 bpod and 400 mcfpd with a flowing tubing pressure of 1,831 psi. We will record a pre-tax charge during the second quarter of fiscal year 2004 of approximately $8.6 million related to the unsuccessful efforts to complete in the lower formation, and we expect the completed well to be on-line in the fourth quarter of 2004. We have also spudded the State Lease 17376 #1 ("Fleur #2") adjacent to the Fleur #1 to test for middle Miocene sands. We expect drilling operations on the Fleur #2 to be completed during the third quarter of 2004.

An investment in our common stock involves risks. You should carefully consider the following risk factors together with the other information contained in this prospectus or in any document incorporated by reference into this prospectus before you decide to buy our common stock. If any of these risks actually occur, our business, financial condition, operating results or cash flows could be materially adversely affected. This could cause the trading price of our common stock to decline and you may lose part or all of your investment.

Our exploration activities subject us to greater risks than development activities

While our acquisition of Southwest provides us with a more balanced drilling portfolio, we continue to focus on exploration activities. For 2004, more than 78% of our currently planned capital expenditures, excluding acquisitions, will be on exploratory prospects. Generally, exploration activities have greater risk than development activities. Development activities relate to increasing oil or natural gas production from an area that is know to be productive by drilling additional wells, working over and recompleting existing wells and other production enhancement techniques. Exploration activities involve the drilling of wells in areas where there is little or no known production. Exploration projects are identified through subjective analysis of geological and geophysical data, including the use of 3-D seismic and other available technology. By comparison, the identification of development prospects is significantly based upon existing production surrounding or adjacent to the proposed drilling site.

Our exploration activities subject us to a greater risk of drilling dry holes or not finding oil or natural gas that can be produced economically. The seismic data and other technology we use does not allow us to know with certainty prior to drilling a well whether oil or natural gas is present or can be produced economically. In 2003, 10 gross (8.8 net) of the 16 gross (12.7 net) wells drilled and completed in south Louisiana and the Cotton Valley Reef Complex were dry holes, and we were unsuccessful in completing the lower formations of our Fleur #1 well, resulting in a pre-tax charge of $8.6 million in the second quarter of 2004. We cannot assure you that

any of our future exploration efforts will be successful, and if such activities are unsuccessful, it will have a significant adverse affect on our results of operations, cash flow and capital resources.

If we do not replace reserves we produce, our financial results will suffer

In general, the volume of production from an oil and gas property declines as reserves related to that property are depleted. The decline rates depend upon reservoir characteristics. Historically, our oil and gas properties have had steep rates of decline and short estimated productive lives. The average productive life of our reserves at December 31, 2003 was approximately 3.6 years, based on 2003 production levels. This is down from 5.9 years at December 31, 2002, based on 2002 production levels. During 2003, we replaced 28% of our 2003 net production through extensions and discoveries. After adjusting our reserves for downward revisions of previous estimates, we realized a net replacement of only 5% of our 2003 net production. In 2002, we replaced 207% of our 2002 net production, consisting of 119% from acquisitions of proved properties, 70% from upward revisions of previous estimates and 18% from extensions and discoveries.

Our oil and gas reserves will decline as they are produced unless we are able to conduct successful exploration and development activities or acquire additional properties with proved reserves. The Southwest acquisition in 2004 significantly extended the estimated productive life of our reserves. We estimate that the average life of reserves acquired through the Southwest acquisition is 16.2 years and that the average productive life of our reserves on a combined basis is 6.6 years. However, because we continue to engage in exploration activities, we are subject to a higher level of risk that we will be unsuccessful in replacing produced reserves. If we do not replace our production with new reserves over time, we will liquidate our reserves, which could affect our liquidity and capital resources. We cannot assure you that we can successfully find and produce reserves economically or acquire additional proved reserves at acceptable costs in the future.

Acquisitions are subject to the risks and uncertainties of evaluating reserves and potential liabilities and may be disruptive and difficult to integrate into our business

Acquired properties, like those we acquired in the Southwest transaction, can be subject to significant unknown liabilities. Prior to completing an acquisition, we generally do not conduct a detailed review of each individual property to be acquired in an acquisition. Even a detailed review or inspection of each property may not reveal all existing or potential liabilities associated with owning or operating the property. Moreover, some potential liabilities, such as environmental liabilities related to groundwater contamination, may not be discovered even when a review or inspection is performed.

Our initial reserve estimates for acquired properties may be inaccurate. Downward adjustments to our estimated proved reserves, including reserves added through acquisitions, could require us to write down the carrying value of our oil and gas properties, which would reduce our earnings and our stockholders' equity.

Our failure to integrate Southwest or other acquired businesses successfully into our existing business could result in our incurring unanticipated expenses and losses. In addition, we may have to assume cleanup or reclamation obligations or other unanticipated liabilities in connection with these acquisitions. The scope and cost of these obligations may ultimately be materially greater than estimated at the time of the acquisition.

The process of integrating acquired operations into our existing operations may result in unforeseen operating difficulties and may require significant management attention and financial resources that would otherwise be available for the ongoing development or expansion of existing operations.

We are highly leveraged and our significant indebtedness could limit our ability to successfully operate our business

We currently have a high level of debt. Our ratio of long-term debt to total capitalization at March 31, 2004 increased from 34% to 62% on a pro forma basis. Our exploration and development program will require substantial capital resources, estimated to be approximately $94 million in 2004, and our existing operations will also require ongoing capital expenditures. In addition, if we decide to pursue additional acquisitions, our capital expenditures will increase both to complete such acquisitions and to explore and develop any newly acquired properties. The degree to which we are leveraged could have other important consequences, including the following:

To the extent we incur additional indebtedness in the future, these risks could intensify.

Any failure to meet our debt obligations could harm our business, financial condition and results of operation. If our cash flow and capital resources are insufficient to fund our debt obligations, we may be forced to sell assets, seek additional equity or debt capital or restructure our debt. In addition, any failure to make scheduled payments of interest and principal on our outstanding indebtedness would likely result in a reduction of our credit rating, which could harm our ability to incur additional indebtedness on acceptable terms. Our cash flow and capital resources may be insufficient to meet scheduled payments of interest and principal in the future, including payments under our bank credit facility, and any such alternative measures may be unsuccessfully or may not permit us to meet scheduled debt service obligations, which could cause us to default on our obligations and impair our liquidity.

Our liquidity, including the availability of capital resources, is uncertain

Our current cash flow forecasts indicate that the amount of funds available to us under our bank credit facility combined with our anticipated operating cash flow will be sufficient to finance our capital expenditures, excluding acquisitions, and will provide us with adequate liquidity at least the next twelve months. Although we believe the assumptions and estimates made in our forecasts are reasonable events, such as those described below, could cause the borrowing base under our bank credit facility to be less than expected, cash flow to be less than expected or capital expenditures to be more than expected.

Adverse changes in reserve estimates or commodity prices could reduce our borrowing base. The banks establish the borrowing base at least twice annually by preparing a reserve report using price-risk assumptions they believe are proper under the circumstances. Any adverse changes in estimated quantities of reserves, the pricing parameters being used or the risk factors being applied since the date of the last borrowing base determination could lower the borrowing base under our bank credit facility. If our outstanding debt exceeds our borrowing base, we will not be able to borrow any additional funds, and we will be required to repay the excess or convert the debt to a term note. Without availability under credit facility, we may be unable to meet our obligations as they mature.

Shortfalls or delays in production or declines in commodity prices could reduce our cash flow from operating activities. We rely on estimates of reserves to forecast our cash flow from operating activities. If the production from those reserves is delayed or is lower than expected, our cash flow from operating activities may be lower than we anticipated. Commodity prices also impact our cash flow from operating activities.

Delays in bringing successful wells on production may reduce our liquidity. As a general rule, we experience a significant lag time between the initial cash outlay on a prospect and the inclusion of any value for such prospect in the borrowing base under the our bank credit facility. Until a well is on production, the banks may assign only a minimal borrowing base value to the well, and cash flow from the well are not available to fund our operating expense. Delays in bringing wells on production may reduce the borrowing base significantly, depending on the amounts borrowed and the length of the delays.

Volatility of oil and gas prices significantly affects our cash flow and capital resources and our ability to produce oil and gas economically

Historically, the markets for oil and gas have been volatile, and we believe that they are likely to continue to be volatile. Significant changes in oil and gas prices may result from relatively minor changes in the supply of and demand for oil and natural gas, market uncertainty and other factors that are beyond our control. We cannot predict, with any degree of certainty, future oil and natural gas prices. Recent historic highs for both oil and gas prices have positively affected our earnings and financial condition, but we do not expect oil and gas prices to remain at these levels.

Changes in oil and natural gas prices significantly affect our revenues, operating results, profitability and the value of our oil and gas reserves. Those prices also affect the amount of cash flow available for capital expenditures, our ability to borrow money or raise additional capital and the amount of oil and natural gas that we can produce economically. The amount we can borrow under our bank credit facility is subject to periodic redeterminations based in part on current prices for oil and natural gas at the time of the redetermination.

Changes in oil and gas prices impact both our estimated future net revenue and the estimated quantity of proved reserves. Price increases may permit additional quantities of reserves to be produced economically, and price decreases may render uneconomic the production of reserves previously classified as proved. Thus, we may experience material increases and decreases in reserve quantities solely as a result of price changes and not as a result of drilling or well performance.

Hedging transactions may limit our potential gains and involve other risks

We attempt to optimize the price we receive for our oil and gas production while maintaining a prudent hedging program to mitigate our exposure to declining product prices. This strategy means that within the framework of a comprehensive hedging program, we sometimes terminate a hedge when we believe that market factors indicate there could be an increase in product prices that we would not realize with the hedge in place. While we attempt to make informed market decisions on the termination of hedges, this strategy may sometimes expose us to downside risk that would not have existed otherwise.

Information concerning our reserves and future net reserve estimates is inherently uncertain

Estimates of our proved reserves and the estimated future net revenues from such reserves are based upon various assumptions including assumptions required by the SEC relating to oil and gas prices, drilling and operating expenses and other matters. The process of estimating oil and gas reserves requires significant decisions and assumptions in the evaluation of available geological, geophysical, engineering and economic data for each reservoir. The interpretation of this data is a subjective process dependent upon the quality of the data and the decision-making and judgment of reservoir engineers. Estimates prepared by different engineers or by the same engineers at different times may vary substantially. Therefore, the estimates of our oil and gas reserves are inherently imprecise.

Actual future production, oil and gas prices, revenues, taxes, development expenditures, operating expenses and quantities of recoverable oil and gas reserves will most likely vary from the assumptions we make in estimating reserves. Any significant variance could materially affect the estimated quantities and value of our oil and gas reserves, which in turn may adversely affect our cash flow, results of operations and the availability of capital resources. In addition, we may adjust estimates of proved reserves to reflect production history, results of exploration and development, prevailing oil and gas prices and other factors, many of which are beyond our control.

You should not assume that the present value of proved reserves is equal to the current fair market value of our estimated oil and gas reserves. In accordance with the requirements of the SEC, the estimated discounted future net cash flows from proved reserves are generally based on prices and costs as of the date of the estimate. Actual future prices and costs may be materially higher or lower than those as of the date of the estimate. The timing of both the production and the expenses with respect to the development and production of oil and gas properties will effect the timing of future net cash flows from proved reserves and their present value.

The estimated proved reserve information is based in part upon reserve reports prepared by independent engineers. From time to time, estimates of our reserves are also made by the banks in establishing the borrowing base under our bank credit facility and by our engineers for use in developing business plans and making various decisions. Such estimates may vary significantly and have a material effect upon our business decisions and available capital resources.

Our proved reserves are concentrated in limited geographic areas, exposing us to adverse developments with respect to a single well or area of operations

Our proved developed reserves are concentrated in a limited number of fields and properties. At December 31, 2003, prior to the Southwest acquisition, our top nine producing wells represented approximately 34% of our estimated proved reserves. In addition, substantially all of our estimated present value of proved reserves are located in four geographic areas: the Austin Chalk (Trend); the Cotton Valley Reef Complex area; south Louisiana; and the Permian Basin. Such concentration of reserves makes us more susceptible to adverse developments with respect to any single well or area of operations and substantially dependent upon a few selected oil and gas properties. An adverse event related to a single well or geographic area may have a significant adverse effect on our reserves, production, cash flow and general financial condition. Substantially all of Southwest's properties are in the Permian

Basin. We do not believe that any individual well acquired from Southwest is material to us. Therefore, as a result of the Southwest acquisition, we believe that our reserves are less concentrated in our top producing wells.

By extending credit to our customers, we are exposed to potential economic loss

We sell our oil and natural gas production to various customers, serve as operator in the drilling, completion and operation of oil and gas wells, and enter into derivatives with various counterparties. As appropriate, we obtain letters of credit to secure amounts due from our principal oil and gas purchasers and follow other procedures to monitor credit risk from joint owners and derivatives counterparties. In 2003, we increased the allowance for doubtful accounts related to amounts due from joint interest owners by approximately $900,000. We cannot assure you that we will not suffer any economic loss related to credit risks in the future.

Drilling oil and natural gas wells is a high-risk activity and subjects us to a variety of factors that we cannot control

Drilling oil and natural gas wells, including development wells, involves numerous risks, including the risk that we may not encounter commercially productive oil or natural gas reservoirs. We may not recover all or any portion of our investment in new wells. The presence of unanticipated pressures or irregularities in formations, miscalculations or accidents may cause our drilling activities to be unsuccessful and result in a total loss of our investment. In addition, we often are uncertain as to the future cost or timing of drilling, completing and operating wells. Further, our drilling operations may be curtailed, delayed or canceled as a result of a variety of factors, including:

Our business depends on oil and natural gas transportation facilities, most of which are owned by others

The marketability of our oil and natural gas production depends in large part on the availability, proximity and capacity of pipeline systems owned by third parties. The unavailability of or lack of available capacity on these systems and facilities could result in the shut-in of producing wells or the delay or discontinuance of drilling plans for properties. Although we have some contractual control over the transportation of our product, material changes in these business relationships could materially affect our operations. Federal and state regulation of oil and natural gas production and transportation, tax and energy policies, changes in supply and demand, pipeline pressures, damage to or destruction of pipelines and general economic conditions could adversely affect our ability to produce, gather and transport oil and natural gas.

Competition in all areas of our operations is intense. The oil and gas industry as a whole also competes with other industries in supplying the energy and fuel requirements of industrial, commercial and individual consumers. In addition, we experience competition from major and independent oil and gas companies and oil and gas syndicates in bidding for desirable oil and gas properties, as well as in acquiring the equipment, data and labor required to operate and develop such properties. A number of our competitors have financial resources and acquisition, exploration and development budgets that are substantially greater than ours, which may adversely affect our ability to compete with these companies. Such companies may be able to pay more for productive oil and gas properties and exploratory prospects and to define, evaluate, bid for and purchase a greater number of properties and prospects than our financial or human resources permit.

The market for our oil, gas and natural gas liquids production depends on factors beyond our control, including domestic and foreign political conditions, the overall level of supply of and demand for oil, gas and natural gas liquids, the price of imports of oil and gas, weather conditions, the price and availability of alternative fuels, the proximity and capacity of gas pipelines and other transportation facilities and overall economic conditions.

Weather, unexpected subsurface conditions and other unforeseen operating hazards may adversely impact our oil and gas activities

Our operations are subject to the usual hazards incident to the drilling and production of oil and gas, such as blowouts, cratering, explosions, uncontrollable flows of oil, gas or well fluids, fires and pollution and other environmental risks. These hazards can cause personal injury and loss of life, severe damage to and destruction of property and equipment, pollution or environmental damage and suspension of operations.

Compliance with environmental and other government regulations could be costly and could negatively impact production

Our oil and gas exploration, production and related operations are subject to extensive rules and regulations promulgated by federal, state and local agencies. Failure to comply with such rules and regulations can result in substantial penalties. The regulatory burden on the oil and gas industry increases our cost of doing business and affects our profitability. Because such rules and regulations are frequently amended or reinterpreted, we are unable to predict the future cost or impact of complying with such laws.

All of the states in which we operate generally require permits for drilling operations, drilling bonds and reports concerning operations and impose other requirements relating to the exploration and production of oil and gas. Such states also have statutes or regulations addressing conservation matters, including provisions for the unitization or pooling of oil and gas properties, the establishment of maximum rates of production from oil and gas wells and the spacing, plugging and abandonment of such wells. The statutes and regulations of certain states also limit the rate at which oil and gas can be produced from our properties.

The Federal Energy Regulatory Commission ("FERC") regulates interstate natural gas transportation rates and service conditions, which affect the marketing of gas we produce, as well as the revenues we receive for sales of such production. Since the mid-1980s, the FERC has issued various orders that have significantly altered the marketing and transportation of gas. These orders resulted in a fundamental restructuring of interstate pipeline sales and transportation services, including the unbundling by interstate pipelines of the sales, transportation, storage and other components of the city-gate sales services such pipelines previously performed. These FERC actions were designed to increase competition within all phases of the gas industry. The interstate regulatory framework may enhance our ability to market and transport our gas, although it may also subject us to greater competition and to the more restrictive pipeline imbalance tolerances and greater associated penalties for violation of such tolerances.

Our sales of oil and natural gas liquids are not presently regulated and are made at market prices. The price we receive from the sale of those products is affected by the cost of transporting the products to market. The FERC has implemented regulations establishing an indexing system for transportation rates for oil pipelines, which, generally, would index such rate to inflation, subject to certain conditions and limitations. We are not able to predict with any certainty what effect, if any, these regulations will have on us, but, other factors being equal, the regulations may, over time, tend to increase transportation costs which may have the effect of reducing wellhead prices for oil and natural gas liquids.

Clayton W. Williams beneficially owns, either individually or through his affiliates, approximately 48% of the outstanding shares of our common stock. Mr. Williams is also the Chairman of the Board and Chief Executive Officer. As a result, Mr. Williams has significant influence in matters voted on by our shareholders and in management decisions. Mr. Williams effectively controls the election of our Board members through his ownership of our common stock. Mr. Williams actively participates in all facets of our business and has a significant impact on both our business strategy and daily operations. This concentration of ownership may discourage a potential acquiror from making an offer to buy our company that other stockholders might find favorable which, in turn, could adversely affect the market price of our common stock. The retirement, incapacity or death of Mr. Williams, or any change in the power to vote his shares, could result in negative market or industry perception and could have a material adverse effect on the market price of our common stock or on our business.

Certain anti-takeover provisions in our charter may discourage potential acquirors

Provisions of our certificate of incorporation and bylaws and Delaware law may have the effect of discouraging unsolicited takeover proposals for the Company. Our board of directors is divided into three classes, with the directors of each class serving

staggered terms of three years each or until their respective successors are elected and qualified. Under our certificate of incorporation, our board of directors may issue serial preferred stock with such rights and preferences as the board may determine, without stockholder approval. The Delaware General Corporation Law imposes additional restrictions on business combinations with certain interested parties.

The selling stockholders will receive all of the proceeds from the sale of common stock under this prospectus.

We are registering all 1,380,869 shares of common stock covered by this prospectus on behalf of the selling stockholders named in the table below. We issued all of these shares to the selling stockholders in a private placement transaction. We are registering the shares in order to permit the selling stockholders to offer the shares for resale from time to time. The selling stockholders may sell all, some or none of the shares covered by this prospectus. See "Plan of Distribution."

The following table lists the selling stockholders and other information regarding the ownership of common stock by each of the selling stockholders as of June 21, 2004:

The selling stockholders (or, subject to applicable law, their pledges, donees, distributes, transferees, or successors in interest) are offering shares of our common stock that they acquired from us in a private placement transaction. This prospectus covers the resale by the selling stockholders of up to 1,380,869 shares of common stock.

In connection with our issuance to the selling stockholders of our common stock in the private placement, we are filing a registration statement on Form S-3 with the Securities and Exchange Commission, or SEC. The registration statement covers the resale of the common stock from time to time as indicated in this prospectus. This prospectus forms a part of that registration statement. We have also agreed to prepare and file any amendments and supplements to the registration statement as may be necessary to keep it effective for a period not to exceed two years and to indemnify and hold the selling stockholders harmless against certain liabilities under the Securities Act of 1933 that could arise in connection with the selling stockholders' sale of the shares covered by this prospectus. We have agree to pay all reasonable fees and expenses incident to the filing of the registration statement, but the selling stockholders will pay any brokerage commissions, discounts or other expenses relating to the sale of the common stock.

The selling stockholders may sell the shares of common stock described in this prospectus directly or through underwriters, brokers, dealers or agents. The selling stockholders may also transfer, devise or gift these shares by other means not described in this prospectus. As a result, pledgees, donees, transferees or other successors in interest that receive such shares as a gift, partnership distribution or other non-sale related transfer may offer shares of the common stock covered by this prospectus. In addition, if any shares covered by this prospectus qualify for sale pursuant to Rule 144 under the Securities Act of 1933, the selling shareholders may sell such shares under Rule 144 rather than pursuant to this prospectus.

The selling stockholders may sell shares of common stock from time to time in one or more transactions:

The selling stockholders may offer their shares of common stock in one or more of the following transactions:

In effecting sales, brokers or dealers engaged by the selling stockholders may arrange for other brokers or dealers to participate in the resales. The selling stockholders may enter into hedging transactions with brokers or dealers, and in connection with those transactions, brokers or dealers may engage in short sales of the shares. The selling stockholders also may sell shares short and deliver the shares to close out such short positions, provided that the short sale is made after the registration statement has been declared effective and a copy of this prospectus is delivered in connection with the short sale. The selling stockholders also may enter into option or other transactions with broker-dealers that require the delivery to the brokers or dealers of the shares, which the brokers or dealers may resell pursuant to this prospectus. The selling shareholders also may pledge the shares to a broker or dealer, and upon a default, the broker or dealer may effect sales of the pledge shares pursuant to this prospectus.

The SEC may deem the selling stockholders and any underwriters, brokers, dealers or agents that participate in the distribution of the shares of common stock to the "underwriters" within the meaning of the Securities Act. The SEC may deem any profits on the resale of the shares of common stock and any compensation received by any underwriter, broker-dealer or agent to be underwriting discounts and commissions under the Securities Act. Each selling stockholder has purchased the common stock in the ordinary course of its business, and at the time the selling stockholder purchased the common stock it was not a party to any agreement or other understanding to distribute the securities, directly or indirectly.

Under the Securities Exchange Act of 1934, any person engaged in the distribution of the shares of common stock may not simultaneously engage in market-making activities with respect to the common stock for five business days prior to the start of the distribution. In addition, each selling shareholder and any other person participating in a distribution will be subject to the Securities Exchange Act of 1934, which may limit the timing of purchases and sales of common stock by the selling shareholder or any such other person.

The validity of the common stock offered under this prospectus will be passed upon by Vinson & Elkins L.L.P., Austin, Texas.

The consolidated financial statements of the Company as of December 31, 2003 and 2002, and for each of the years in the three-year period ended December 31, 2003, have been incorporated by reference herein in reliance upon the report of KPMG LLP, an independent registered public accounting firm, incorporated by reference herein, and upon the authority of said firm as experts in accounting and auditing. The audit report covering the December 31, 2003, consolidated financial statements refers to a change in the method of accounting for abandonment obligations in accordance with Statement of Financial Accounting Standards No. 143 "Accounting for Asset Retirement Obligations" as of January 1, 2003, and a change in method of accounting for derivative instruments in accordance with Statement of Financial Accounting Standards No. 133 "Accounting for Derivative Instruments and Hedging Activities" as of January 1, 2001.

The consolidated financial statements of Southwest as of December 31, 2003 and 2002, and for each of the years in the three-year period ended December 31, 2003, have been incorporated by reference herein in reliance upon the report of KPMG LLP, an independent registered public accounting firm, incorporated by reference herein, and upon the authority of said firm as experts in accounting and auditing. The audit report covering the December 31, 2003, consolidated financial statements refers to a change in the method of accounting for abandonment obligations in accordance with Statement of Financial Accounting Standards No. 143 "Accounting for Asset Retirement Obligations" as of January 1, 2003, a change in the method of computing depletion as of January 1, 2002, and a change in method of accounting for derivative instruments in accordance with Statement of Financial Accounting Standards No. 133 "Accounting for Derivative Instruments and Hedging Activities" as of January 1, 2001.

The estimates of proved reserves, estimated future net revenues and present value thereof incorporated by reference in this prospectus to our Annual Report on Form 10-K for the year ended December 31, 2003 have been derived from the reports of Williamson Petroleum Consultants, Inc., independent petroleum engineers, and all such information has been so included in reliance on the authority of such firm as experts regarding the matters contained in their reports.

We file annual, quarterly and current reports, proxy statements and other information with the SEC, under the Securities and Exchange Act of 1934. You may read and copy this information at the SEC's Public Reference Room at 450 Fifth Street, N.W., Washington, D.C. 20549. You may also obtain copies of these documents at prescribed rates from the Public Reference Section of the SEC at its Washington address. Please call the SEC at 1-800-SEC-0330 for further information.

This prospectus is part of a registration statement on Form S-3 that we have filed with the SEC. This prospectus does not contain all of the information we have included in the registration statement and the accompanying exhibits and schedules as permitted by the rules and regulations of the SEC. The registration statement, exhibits and schedules are available at the SEC's public reference room or through its website.

The SEC allows us to "incorporate by reference" the information we file with it, which means that we disclose important information to you by referring you to another document filed separately with the SEC. The information incorporated by reference is deemed to be part of this prospectus, except for any such information superseded by information contained directly in this prospectus or by information contained in a later filed document incorporated by reference. This prospectus incorporates by reference the documents set forth below that we have previously filed with the SEC. These documents contain important information about us and our financial condition.

Clayton Williams Energy, Inc. SEC Filings (SEC File No. 0-20838)		Period
The description of our common stock as set forth in our Registration Statement on Form S-2 (Registration No. 333-13441), including any amendments or reports filed for purposes of updating such description.		Filed October 4, 1996
Annual Report on Form 10-K		Fiscal year ended December 31, 2003, filed March 11, 2004
Quarterly Reports on Form 10-Q		Quarterly period ended March 31, 2004, filed May 5, 2004
Current Report on Form 8-K		Filed on May 7, 2004
Current Report on Form 8-K		Filed on May 20, 2004
Current Report on Form 8-K		Filed on May 21, 2004
Current Report on Form 8-K		Filed May 25, 2004
Current Report on Form 8-K		Filed June 3, 2004
Current Report on Form 8-K		Filed June 23, 2004

You may request a copy of these filings, at no cost, by writing or calling us at the following address or telephone number:

Clayton Williams Energy, Inc.
6 Desta Drive, Suite 6500
Midland, Texas 79750-5510
(432) 682-6324
Attn: Investor Relations

We are also incorporating by reference all documents filed with the SEC by us pursuant to sections 13(a), 13(c), 14 or 15(d) of the Securities Exchange Act of 1934 subsequent to the date of this prospectus and prior to termination of the offering made hereby. Any statement contained in a document incorporated or deemed to be incorporated by reference in this prospectus shall be deemed to be modified or superseded for purposes of this prospectus to the extent that a statement contained in any other subsequently filed document which also is or is deemed to be incorporated by reference in this prospectus modifies or supersedes such statement.

YOU SHOULD RELY ONLY ON THE INFORMATION CONTAINED IN THIS PROSPECTUS OR INCORPORATED BY REFERENCE. WE HAVE NOT AUTHORIZED ANYONE TO PROVIDE YOU WITH INFORMATION DIFFERENT FROM THAT CONTAINED IN THIS PROSPECTUS. THE STATEMENTS AND REPRESENTATIONS CONTAINED WITHIN THIS PROSPECTUS ARE MADE AS OF THE DATE INDICATED ON THE COVER PAGE. THE DELIVERY OF THIS PROSPECTUS DOES NOT, UNDER ANY CIRCUMSTANCES, CREATE THE IMPLICATION THAT THERE HAS BEEN NO CHANGE SINCE THAT DATE.

THIS PROSPECTUS IS NOT AN OFFER TO SELL OR A SOLICITATION OF AN OFFER TO BUY ANY SECURITIES OTHER THAN THOSE REGISTERED SECURITIES TO WHICH THE PROSPECTUS RELATES. MOREOVER, THIS PROSPECTUS DOES NOT CONSTITUTE AN OFFER TO SELL OR A SOLICITATION OF AN OFFER TO BUY IN ANY CIRCUMSTANCES IN WHICH SUCH AN OFFER OR SOLICITATION IS UNLAWFUL.

The following table sets forth the estimated expenses payable by the registrant in connection with the issuance and distribution of the securities being registered. All amounts shown are estimates, except the registration fee.

Securities and Exchange Commission registration fee		$	4,201
Legal fees and expenses			[ ]
Printing expenses			[ ]
Accounting fees and expenses			[ ]
Printing expenses			[ ]
Miscellaneous			[ ]
	Total	$	[ ]

We have agreed to pay all fees and expenses incident to the registration of the shares.

Subsection (a) of Section 145 of the Delaware General Corporation Law, or DGCL, empowers a corporation to indemnify any person who was or is a party or is threatened to be made a party to any threatened, pending or completed action, suit or proceeding whether civil, criminal, administrative or investigative (other than an action by or in the right of the corporation) by reason of the fact that the person is or was a director, officer, employee or agent of the corporation, or is or was serving at the request of the corporation as a director, officer, employee or agent of another corporation, partnership, joint venture, trust or other enterprise, against expenses (including attorneys' fees), judgments, fines and amounts paid in settlement actually and reasonably incurred by the person in connection with such action, suit or proceeding if the person acted in good faith and in a manner the person reasonably believed to be in or not opposed to the best interests of the corporation, and, with respect to any criminal action or proceeding, had no reasonable cause to believe the person's conduct was unlawful.

Subsection (b) of Section 145 empowers a corporation to indemnify any person who was or is a party or is threatened to be made a party to any threatened, pending or completed action or suit by or in the right of the corporation to procure a judgment in its favor by reason of the fact that such person acted in any of the capacities set forth above, against expenses (including attorneys' fees) actually and reasonably incurred by the person in connection with the defense or settlement of such action or suit if the person acted in good faith and in a manner the person reasonably believed to be in or not opposed to the best interests of the corporation, except that no indemnification shall be made in respect to any claim, issue or matter as to which such person shall have been adjudged to be liable to the corporation unless and only to the extent that the Court of Chancery or the court in which such action or suit was brought shall determine upon application that, despite the adjudication of liability but in view of all the circumstances of the case, such person is fairly and reasonably entitled to indemnity for such expenses which the Court of Chancery or such other court shall deem proper.

Section 145 further provides that to the extent a director or officer of a corporation has been successful on the merits or otherwise in the defense of any such action, suit or proceeding referred to in subsections (a) and (b) of Section 145 or in the defense of any claim, issue or matter therein, he shall be indemnified against expenses (including attorneys' fees) actually and reasonably incurred by him in connection therewith; that the indemnification provided for by Section 145 shall not be deemed exclusive of any other rights which the indemnified party may be entitled; that indemnification provided by Section 145 shall, unless otherwise provided when authorized or ratified, continue as to a person who has ceased to be a director, officer, employee or agent and shall inure to the benefit of such person's heirs, executors and administrators; and empowers the corporation to purchase and maintain insurance on behalf of a director or officer of the corporation against any liability asserted against him and incurred by him in any such capacity, or arising out of his status as such, whether or not the corporation would have the power to indemnify him against such liabilities under Section 145.

Section 102(b)(7) of the DGCL provides that a certificate of incorporation may contain a provision eliminating or limiting the personal liability of a director to the corporation or its stockholders for monetary damages for breach of fiduciary duty as a director, provided that such provision shall not eliminate or limit the liability of the director:

In accordance with Section 102(b)(7), Article VI of our Second Restated Certificate of Incorporation, as amended, provides that, in general, no director of the registrant shall be personally liable to us or our stockholders for monetary damages for breach of fiduciary duty as a director, except for liability (i) for any breach of the director's duty of loyalty to the Company or its stockholders, (ii) for acts or omissions not in good faith or which involve intentional misconduct or a knowing violation of law, (iii) under Section 174 of the General Corporation Law of the State of Delaware, or (iv) for any transaction from which the director derived an improper personal benefit.

In addition, Article IX of our Second Restated Certificate of Incorporation, as amended, and Article VI of our Bylaws provide, in general, that we shall indemnify each of our directors and officers against expenses, judgments, fines and amounts paid in settlement actually and reasonably incurred by such person in connection with any third party proceeding if such person acted in good faith and in a manner such person reasonably believed to be in, or not opposed to, our best interests and, with respect to any criminal third party proceeding, had no reasonable cause to believe such conduct was unlawful.

Exhibit Number		Exhibit Title
2.1		Agreement and Plan of Merger among Clayton Williams Energy, Inc., CWEI-SWR, Inc. and Southwest Royalties, Inc., dated May 3, 2004 (Incorporated by reference to Exhibit 2.1 to the Company's Current Report on Form 8-K filed on June 3, 2004).
		* All schedules to this Exhibit 2.1 filed herewith have been omitted in accordance with Item 601(b)(2) of Regulation S-K. The Company will furnish supplementally a copy of any omitted schedule to the Commission upon request.
3.1		Second Restated Certificate of Incorporation of the Company (Incorporated by reference to Exhibit 2.1 to the Company's Registration Statement on Form S-2, dated October 4, 1996, Registration No. 333-13441).
3.2		Certificate of Amendment of Second Restated Certificate of Incorporation of Clayton Williams Energy, Inc. (Incorporated by reference to Exhibit 3.1 to the Company's Form 10-Q for the period ended September 30, 2000 filed on November 14, 2000).
3.3		Bylaws of the Company (Incorporated by reference to Exhibit 3.4 to the Company's Registration Statement on Form S-1 dated August 22, 1995, Registration No. 33-43350).
4.1		Form of Stock Purchase Agreement dated May 19, 2004 by and among the Company and the selling stockholders (Incorporated by reference to Exhibit 4 to the Company's Current Report on Form 8-K filed on June 2, 2004).
*5.1		Opinion of Vinson & Elkins L.L.P.
*23.1		Consent of Independent Registered Public Accounting Firm (relating to Clayton Williams Energy, Inc.)
*23.2		Consent of Independent Registered Public Accounting Firm (relating to Southwest Royalties, Inc.)
*23.3		Consent of Vinson & Elkins L.L.P. (included in Exhibit 5.1 hereto)
*23.4		Consent of Williamson Petroleum Consultants, Inc.
*24.1		Powers of Attorney (included on the signature pages of this Registration Statement)

(c) That, for purposes of determining any liability under the Securities Act, each filing of the registrant's annual report pursuant to Section 13(a) or Section 15(d) of the Exchange Act (and, where applicable, each filing of an employee benefits plan's annual report pursuant to Section 15(d) of the Exchange Act) that is incorporated by reference in the registration statement shall be deemed to be a new registration statement relating to the securities offered therein, and the offering of such securities at that time shall be deemed to be the initial bona fide offering thereof.

(d) Insofar as indemnification for liabilities arising under the Securities Act may be permitted to directors, officers and controlling persons of the registrant pursuant to any charter provision, by-law, contract, arrangement, statute, or otherwise, each registrant has been advised that in the opinion of the Commission such indemnification is against public policy as expressed in the Securities Act and is, therefore, unenforceable. In the event that a claim for indemnification against such liabilities (other than the payment by the registrant of expenses incurred or paid by a director, officer or controlling person of the registrant in the successful defense of any action, suit or proceeding) is asserted against the registrant by such director, officer or controlling person in connection with the securities being registered, the registrant will, unless in the opinion of counsel the matter has been settled by controlling precedent, submit to a court of appropriate jurisdiction the question of whether such indemnification by it is against public policy as expressed in the Securities Act and will be governed by the final adjudication of such issue.

Pursuant to the requirements of the Securities Act of 1933, the registrant certifies that it has reasonable grounds to believe that it meets all of the requirements for filing on Form S-3 and has duly caused this registration statement to be signed on its behalf by the undersigned, thereunto duly authorized, in the City of Midland, State of Texas, on June 24, 2004.

KNOW ALL MEN BY THESE PRESENTS, that each person whose signature appears below constitutes and appoints L. Paul Latham and Mel G. Riggs, and each of them (with full power to each of them to act alone), his or her true and lawful attorney-in-fact and agent, with full power of substitution and resubstitution, for him or her and in his or her name, place and stead, in any and all capacities, to sign on his or her behalf individually and in each capacity stated below any and all amendments (including post-effective amendments) to this Registration Statement, and to file the same, with all exhibits thereto and other documents in connection therewith, with the Securities and Exchange Commission, granting unto said attorneys-in-fact and agents, and each of them, full power and authority to do and perform each and every act and thing requisite and necessary to be done in and about the premises, as fully to all intents and purposes as he or she might or could do in person, hereby ratifying and confirming all that said attorneys-in-fact and agents and either of them, or their substitutes, may lawfully do or cause to be done by virtue hereof.

Pursuant to the requirements of the Securities Act of 1933, this Registration Statement has been signed by the following persons on behalf of the registrant and in the capacities and on the dates indicated.

6 Desta Drive, Suite 6500 Midland, Texas 79705-5510 (432) 682-6324
(Address, including zip code, and telephone number, including area code of registrant's principal executive offices)
Delaware (State or other jurisdiction of incorporation or organization)				74-2396863 (I.R.S. Employer Identification Number)
L. Paul Latham Executive Vice President and Chief Operating Officer Clayton Williams Energy, Inc. 6 Desta Drive, Suite 6500 Midland, Texas 79705-5510 (432) 682-6324
(Name, address, including zip code, and telephone number, including area code, of agent for service)

Title of each class of securities to be registered	Amount to be registered	Proposed maximum offering price per unit(1)	Proposed maximum aggregate offering price(1)	Amount of registration fee


Common Stock, par value $.10 per share	1,380,869 shares	$24.01	$33,154,665	$4,200.69

FORWARD-LOOKING STATEMENTS		1
RECENT DEVELOPMENTS		1
RISK FACTORS		2
USE OF PROCEEDS		8
SELLING STOCKHOLDERS		8
PLAN OF DISTRIBUTION		9
LEGAL MATTERS		10
EXPERTS		10
WHERE YOU CAN FIND MORE INFORMATION		10

				Shares Owned After the Offering(1)
		Number of Shares Owned Prior to Offering
Name of Selling Stockholder			Number of Shares Being Offered
Name of Selling Stockholder			Number of Shares Being Offered	Shares	Percent(2)
Columbia Acorn Fund		440,000	440,000	—	—
Capital Ventures International		217,391	217,391	—	—
State Street Research Small Cap Energy Fund, LLC(3)		200,900	150,000	50,900	*
BBT Fund, L.P.		200,000	200,000	—	—
Raytheon Company Salaried Pension Plan(3)		125,000	40,000	85,000	*
Raytheon Company Combined—DB/DC Master Trust(3)		41,000	20,000	21,000	*
Bellsouth Corporation Master Pension Trust(3)		190,000	50,000	140,000	1.3	%
Portside Growth and Opportunity Fund(4)		100,000	100,000	—	—
Edison Sources Ltd.(3)		60,000	40,000	20,000	*
Concentrated Alpha Partners, L.P.		50,000	50,000	—	—
Bluegrass Growth Fund LP		43,478	43,478	—	—
UBS O'Connor LLC f/b/o O'Connor PIPES Corporate Strategies Master Ltd.		30,000	30,000	—	—
	Total	1,697,769	1,380,869	316,900	2.9	%

Signature	Title	Date

/s/ CLAYTON W. WILLIAMS Clayton W. Williams	Chairman of the Board, President and Chief Executive Officer and Director (principal executive officer)	June 24, 2004
/s/ L. PAUL LATHAM L. Paul Latham	Executive Vice President, Chief Operating Officer and Director	June 24, 2004
/s/ MEL G. RIGGS Mel G. Riggs	Senior Vice President— Finance, Secretary, Treasurer, Chief Financial Officer and Director (principal financial officer)	June 24, 2004
/s/ MICHAEL L. POLLARD Michael L. Pollard	Vice President—Accounting (principal accounting officer)	June 24, 2004
/s/ STANLEY S. BEARD Stanley S. Beard	Director	June 24, 2004
/s/ DAVIS L. FORD Davis L. Ford	Director	June 24, 2004
/s/ ROBERT L. PARKER Robert L. Parker	Director	June 24, 2004
Jordan R. Smith	Director	June , 2004

		CLAYTON WILLIAMS ENERGY, INC.
		By	/s/ MEL G. RIGGS Mel G. Riggs Senior Vice President-Finance and Chief Financial Officer