The effects of acute and chronic cyclophosphamide (CP) exposure to male rats on several neurotransmitter enzymes have been examined in various brain regions of the F1 progeny at 90 d old. The acute postmeiotic CP exposure to male rats induced significant biphasic changes in the choline acetyltransferase (ChAT) activity in various brain regions of F1 progeny; significant decreases in the cerebellar acetylcholinesterase (AChE) activity of the male (47%) and the female (14%) F1 progeny, and moderate decrease (26%) in the hippocampal AChE activity in the female F1 progeny; and a moderate increase (29%) in the temporo-cortical glutamic acid decarboxylase (GAD) activity of the female F1 rats. The chronic CP-exposed male rats resulted in a slight but significant decrease (16%) in the temporo-cortical ChAT activity in the female F1 progeny; a marked increase (51%) in the hypothalamic AChE activity in the male F1 progeny; and a marked decrease (32%) in cerebellar GAD activity and a slight increase (13%) in the striatal GAD activity in the female F1 progeny. These enzymatic changes in the adult brain of F1 progeny of CP-treated males may be associated with the behavioral abnormalities observed previously. Results suggest that these neurochemical parameters may be useful markers for analysis of the potential neurotoxicity of CP.