Maneb, an organomanganese fungicide, is largely used in agricultural regions for control of field crop pathologies. Despite its apparent low toxicity, there are reports showing that maneb has harmful effects on peripheral and central nervous systems. In this work the effects of acute administration of maneb were studied on some experimental animal models. Male adult mice were treated with several doses of maneb, IP, and submitted to gross behavioral observation (200-1000 mg/kg) and measurement of locomotor activity, barbiturate-induced sleeping time, isolation-induced aggressiveness, catatonia, climbing behavior and of rota-rod performance (30, 60 and 100 mg/kg). The results showed that maneb has an inhibitory effect on locomotor activity and aggressiveness and increases barbiturate-induced sleeping time and haloperidol-induced catatonia. However, maneb did not affect the apomorphine-induced climbing behavior of animals. These data indicate that maneb has a CNS depressant-like effect, and suggest, at least partially, the involvement of dopaminergic systems in the mediation of this effect.