Selective bilateral destruction of dopaminergic neuronal terminals in the accumbens nuclei with 6-hydroxydopamine reduced spontaneous and amphetamine-induced locomotor and exploratory behaviour and sniffing activity; amphetamine-induced stereotyped behaviour appeared to be mildly potentiated. Similarly induced bilateral destruction of dopaminergic nerve endings in the caudate-putamen reduced spontaneous activity; amphetamine-induced stereotyped behaviour was abolished. Some animals with severe degrees of neostriatal dopamine depletion were completely unresponsive to amphetamine, apart from intense sniffing activity. Bilateral electrolytic lesions of the accumbens nuclei did not alter spontaneous or amphetamine-induced activity.