Antischizophrenic neuroleptic drugs of the diphenylbutylpiperidine class, which includes pimozide, fluspirilene, penfluridol, and clopimozide, inhibit [3H]nitrendipine binding with IC50 values of 13-30 nM. This inhibition involves receptors for the verapamil/prenylamine class of calcium channel antagonists. These diphenylbutylpiperidines also inhibit potassium-induced calcium-dependent contractions of rat vas deferens at concentrations of 40-350 nM. Other phenothiazine and butyrophenone neuroleptics lack such potent calcium-antagonist actions. Diphenylbutylpiperidines also differ from other neuroleptics in their ability to relieve negative symptoms of schizophrenia, such as emotional withdrawal, as well as the positive symptoms which respond to all neuroleptics. We suggest that these unique antischizophrenic actions are related to a blockade by diphenylbutylpiperidines of voltage-operated calcium channels.