The ability of several neuroleptics to potentiate the inhibitory action of IP administered GABA on the motor activity of mice has been investigated. Haloperidol, chlorpromazine, thioridazine, and clozapine, but not the apparently selective dopamine receptor-blocking agent spiperone, were found to possess such activity. Phenoxybenzamine also proved active in potentiating GABA. Thus blockade of dopamine receptors as well as alpha-adrenergic receptors may be responsible for neuroleptic-induced potentiation of GABA actions.