An open 12-week study was carried out to investigate the use of pimozide (12 mg once daily) as a replacement for antipsychotic maintenance therapy in 30 chronic schizophrenics who had responded poorly to previous neuroleptic monotherapy or polytherapy. After 8 weeks of treatment with pimozide, all 18 symptoms of the Brief Psychiatric Rating Scale were improved from previous treatment values. These differences were statistically significant for conceptual disorganization, depressive mood, hostility and motor retardation. Eleven patients who clearly responded well during the trial and consequently continued pimozide monotherapy were judged, 1 year later, to be functioning as well, or better, than with pre-trial drug treatment.