Approximately 120,000 women of childbearing age used isotretinoin in the first 16 months after its release for the treatment of cystic acne. In September, 1983, the American Academy of Dermatology requested its members to relate the outcome of pregnancies of women inadvertently exposed to isotretinoin ( Accutane ) during pregnancy to its Adverse Drug Reaction Reporting System ( ADRRS ). Of nine pregnancies reported, seven ended in spontaneous abortion or the birth of an infant with birth defects. Of thirty-five pregnancies with isotretinoin exposure reported to the ADRRS or the U.S. Food and Drug Administration, twenty-nine (83%) resulted in spontaneous abortion or infants with birth defects. The most frequently reported severe birth defects involved the central nervous system (microcephaly or hydrocephalus) and the cardiovascular system (anomalies of the great vessels). Microtia or absence of external ears were also noted in a majority of cases. These findings illustrate the usefulness of specialty-based reporting of adverse drug effects and emphasize the teratogenic risk of isotretinoin in humans. Physicians need to fully and carefully inform women of childbearing age of these risks.