Carbon disulfide, a volatile solvent, is widely used in industry. It has been demonstrated that it causes several neuropsychological symptoms. However, the neurochemical basis of its neurotoxic effect is relatively unknown. In this paper we have measured the effect of subacute i.p. administration on neutral and basic aminopeptidase activities in discrete zones of the rat brain using lysine- and leucine-2-naphthylamides as substrates. Neutral aminopeptidase activity showed a significant decrease in the thalamus and cerebellum with marked (not significant) changes in the hypothalamus, hippocampus, medulla, and occipital cortex. There were no changes in basic aminopeptidase activity. It is suggested that aminopeptidase activity could play a role in carbon disulfide neurotoxic action in the aforementioned regions by generating changes in several neuropeptide levels.