In order to investigate the side-effects of crude drugs, twenty drugs have been tested for the teratogenic effect in rats. Among seven drugs contained alkaloid as their ingredients, no one showed teratogenic effect, but Veratri rhizoma showed embryo-toxic as revealed by severe retardation in growth of the fetuses. The other thirteen drugs which have been used freguently in oriental medicines exhibited no teratogenic effect. Cyclophosphamide used as a reference compound showed severe malformation and retardation in the growth of rat fetuses. These findings suggest that the drug extracts adopted for the study might have no teratogenic effect in the rats.