AbstractThe literature pertaining to the effects of drugs on human in‐trauterine development has been reviewed. As far as quality and quantity of reported evidence permits, four categories of drugs were established, namely, those: (1) positively implicated as teratogenic, (2) suspected of having some teratogenic potential, (3) possibly teratogenic under some conditions, and (4) having little or no teratogenic potential under usual conditions of usage. Although a few compounds were judged to belong in each of the first three categories, it was concluded that drugs taken during pregnancy appear in total to make only a small contribution to the causation of human developmental defect