A CCUTANEt* (ROCHE Laboratories, Nutley, New Jersey), known by the generic name “isotretinoin,” is a prescription oral medication approved by the Food and Drug Administration (FDA) to treat severe, recalcitrant nodular acne. It is also a known human teratogen that can cause multiple major malformations. Embryopathy associated with the mother’s exposure to isotretinoin during the first trimester of pregnancy includes craniofacial, cardiac, thymic, and central nervous system malformations. In response to FDA recommendations, the manufacturer began a pregnancyprevention program (PPP) in 1988 that included educational materials for physicians and patients and offered women reimbursement for contraceptive counseling by a physician. The PPP coordinators asked reproductive-aged women being treated with isotretinoin to enroll voluntarily in the Boston University Accutane Survey (BUAS). The total number of reproductive-aged women taking isotretinoin in the United States is unknown; however, 454,273 women enrolled in the BUAS from 1989 to October 1999. BUAS has estimated that 38%-40% of reproductive-aged women taking isotretinoin chose to enroll in the survey (BUAS, unpublished data, 1999). Although isotretinoin is contraindicated in pregnancy and has a package label warning users to avoid pregnancy while taking it, exposed pregnancies occur. Approximately 900 pregnancies occurred among BUAS enrollees during 19891998 (BUAS, unpublished data, 1999). Roche Laboratories began direct-to-consumer print advertisements in 1996, added television and radio advertisements to selected cities in 1997, and expanded the campaign to the entire United States in 1998. During March 1999, CDC interviewed women who had had recent isotretinoin-exposedpregnancies.The objective of the study was to draw attention to the continued occurrence of isotretinoin-exposed pregnancies 11 years after the inception of the PPP and to learn more about why these exposed pregnancies happened. California was selected as the study site because of its large population and the availability of referrals from the California Teratogen Information Service and Clinical Research Center (CTIS). This report summarizes the results of the study, which suggest that some isotretinoin-exposed pregnancies can be prevented. The case reports describe the experiences of three study respondents.