Administration of haloperidol, a common neuroleptic, to pregnant or lactating rats impaired the masculine sex behavior of their male offspring. Prenatal haloperidol did not affect testosterone concentrations in fetuses. Maternal administration of apomorphine, a dopamine agonist, and of alpha-methyl-p-tyrosine, an inhibitor of dopamine synthesis, also demasculinized male offspring. In both experiments other behaviors and developmental milestones were unaffected. Perinatal haloperidol, apomorphine, and alpha-methyl-p-tyrosine did not lower testosterone in adulthood. These drugs may act directly on neurons that control masculine behavior without lowering testosterone prenatally or in adulthood.