Pregnant Wister rats were given daily subcutaneous administrations of methamphetamine (MAPT; varying doses ranging from 1.0 to 4.5mg/kg) from days 7 to20 of gestation and teratogenic effects have been determined. The teratogenic effects inducible with orally administered caffeine (90mg/kg/day)for the same durations were used as the positive controls. MAPT doses greater than 2.0 mg/kg have suppressed the rate of maternal weight gain. Some of the offsprings (F1) of the prenatal MAPT treated groups had decreased growth rate and delayed development of physical characters and functional reflexes. The male offsprings of the MAPT treated groups had significant decreases in their spontaneous motor activity but had enhanced conditioned avoidance responses. However, the mating performances of these offsprings were not affected. These results indicated that prenatal exposure of MAPT may induce some behavioral teratogenicity in rats.