**Exhibit 99.1**    **FOR IMMEDIATE RELEASE**   September 18, 2007 Contact: John Beaver (713) 654-9548  **STERLING CHEMICALS ANNOUNCES LONG-TERM STYRENE SUPPLY AGREEMENT**     HOUSTON, TEXAS, SEPTEMBER 18, 2007 — STERLING CHEMICALS, INC. (SCHI) has announced that onSeptember 17, 2007, it entered into a long-term exclusive styrene supply agreement and a rail carpurchase and sale agreement with NOVA Chemicals Inc. (“Nova”). The effectiveness of theseagreements is conditioned on the approval of the supply agreement by the Federal Trade Commission(the “FTC”). If the supply agreement becomes effective, it will have an initial term extendinguntil December 31, 2017, subject to some limited earlier termination rights held by Sterling. Underthese agreements, Nova will have the exclusive right to the entire production capacity ofSterling’s Texas City, Texas styrene plant, the amount of any styrene supplied being at Nova’soption based on a full-cost formula, and will purchase Sterling’s styrene monomer rail car fleet.In exchange, Nova has agreed to pay Sterling $60 million within ten business days after theagreements become effective. Alternatively, if the FTC does not approve the supply agreement, Novawill be required to pay Sterling a break-up fee of $6 million.*          *          *     Sterling Chemicals, Inc. is a leading North American producer of selected petrochemicals used tomanufacture a wide array of consumer goods and industrial products throughout the world. Itsprimary products are acetic acid, styrene and plasticizers.     The information in this news release relating to matters that are not historical facts constitutesforward-looking information covered by the safe harbor created by Section 27A of the Securities Actof 1933 and Section 21E of the Securities Exchange Act of 1934. The forward-looking information isbased upon current information and expectations regarding Sterling and its subsidiary. Theestimates, forecasts and statements contained in or implied by the forward-looking informationspeak only as of the date on which they are made, are not guarantees of future performance andinvolve certain risks, uncertainties and assumptions that are difficult to evaluate and predict.Therefore, actual outcomes and results could materially differ from what is expressed, implied orforecasted by or in the forward-looking information. Important factors that could cause actualresults to differ materially from what is expressed, implied or forecasted by or in theforward-looking information include the timing and extent of changes in commodity prices and globaleconomic conditions, industry production capacity and operating rates, the supply-demand balancefor Sterling’s products, competitive products and pricing pressures, increases in raw materialcosts, federal and state regulatory developments, Sterling’s high financial leverage, theavailability of skilled personnel and operating hazards attendant to the industry, as well as theother risk factors discussed in Sterling’s filings with the Securities and Exchange Commission,including Sterling’s Annual Report on Form 10-K and Quarterly Reports on Form 10-Q. Sterlingassumes no obligation to update the information contained in this press release.