In July 1998, the US Food and Drug Administration approved the marketing of thalidomide for the treatment of cutaneous manifestations of erythema nodosum leprosum. To ensure that fetal exposure to this teratogenic agent does not occur, the manufacturer has instituted a comprehensive program to control prescribing, dispensing, and use of the drug. This program, known as the System for Thalidomide Education and Prescribing Safety (S.T.E.P.S. [Celgene Corporation, Warren, New Jersey]), is based in part on experience gained with other drugs--specifically isotretinoin and clozapine--that offer important clinical benefits but carry the potential for serious harm. To achieve its goal of the lowest possible incidence of drug-associated teratogenicity, the S.T.E.P.S. program uses a three-pronged approach: (1) controlling access to the drug; (2) educating prescribers, pharmacists, and patients; and (3) monitoring compliance. Clinicians who wish to prescribe thalidomide must be registered in the S.T.E.P.S. Prescriber Registry and agree to prescribe the drug in accordance with S.T.E.P.S. patient eligibility criteria and monitoring procedures. Pharmacies must also register and agree to comply with patient identification and monitoring criteria. Finally, patients receive visual aids, including a videotape, written material, and verbal counseling about the benefits and risks of thalidomide therapy, the importance of not becoming pregnant during therapy, and the types of contraception required (including emergency contraception) and their availability. Women of childbearing potential must agree to undergo pregnancy testing before starting therapy and on a regular schedule during therapy. All patients must agree to complete a confidential survey about their compliance with contraception, testing, and drug therapy. The manufacturer is monitoring survey results and outcome data and is prepared to make whatever modifications to the S.T.E.P.S. program are necessary to ensure its effectiveness. In addition to minimizing the potential risk for fetal harm associated with thalidomide therapy, the S.T.E.P.S. program may provide a model for future cases in which a drug offers compelling benefits but poses profound risks unless its distribution is carefully controlled.