Abstract Chlorpromazine was administered to pregnant rats at doses of 1, 3, or 9 mg/kg/day from Days 6 to 15 of gestation. Fetuses from half the dams were examined for terata, and the remaining litters delivered at term. The growth, morphologic and reflex development, and reproductive performance of the offspring were recorded. Selected males from all groups were tested in the postweaning period for rotorod performance and activity in an open field. At sexual maturity selected pups of both sexes were necropsied; mean organ weights were recorded; and histomorphologic and morphometric examinations were performed on coronal sections of the brain of high-dose and control males. There was no prenatal evidence of a teratogenic effect. The growth, physical, and reflex development of F 1 pups was unaffected during the preweaning period. Postweaning growth of female offspring in all dosage groups was comparable to that of the controls. At 3 and 9 mg/kg/day there was a very slight but statistically significant decrease in average body weight gain of males in the postweaning period, but the biological significance of this effect is uncertain. Mating performance of offspring exposed prenatally to chlorpromazine was unaffected. In the postweaning period there were significant increases in activity in an open field and decreases in latency time in male offspring from the 3 and 9-mg/kg/day dosage groups compared to pooled controls. There were no changes in organ weights and the results of histomorphologic and morphometric examination in brain sections from control and 9-mg/kg/day males were comparable.