Aspartame (APM) at 500 mg/kg per day in drinking water was administered to rats throughout gestation and lactation. In the weanling rats at 20-22 days of age, aminergic neurotransmitter systems were examined. In cerebral cortex, the kinetics of [H-3] clonidine binding to adrenergic alpha2 receptors and of [H-3] ketanserin to serotonergic 5-HT2 receptors were not altered by perinatal exposure to APM. Dopaminergic systems in striatum, studied with [H-3] SCH-23390 and [H-3] spiperone at D1 and D2 receptors respectively, also were not affected. Levels of related amines and their major metabolites in cerebrum and striatum were the same in control weanlings and in weanlings of mothers treated with APM. No influence of APM on body weight changes, litter size, or weanling weights was observed. APM administered in drinking water more closely resembles human ingestion of large amounts of this sweetener in foods and beverages. These studies suggest that consumption of APM during pregnancy and lactation does not affect amine neurotransmitter systems in offspring.