In this study, chronic schizophrenic outpatients who had been maintained on various neuroleptics for an average of about 4 years had their previous medications (approximately equivalent to 695 mg of chlorpromazine per day) changed abruptly to either pimozide or fluphenazine given in single daily oral doses on a double-blind basis for a period of 52 weeks. Average daily doses were pimozide 9.6 mg and fluphenazine 12.5 mg. Measurements of the therapeutic effects of the two drugs were made immediately prior to starting the study, at the end of the 2nd and 4th weeks, and thereafter every 4th week to the end of the study. Three psychometric scales were used for evaluation: Brief Psychiatric Rating Scale (BPRS); Evaluation of Social Functioning (ESFR); and Clinical Global Impressions (CGI). In addition, patients participated in a Social Adjustment Inventory (SAI) evaluation. Statistical analysis with the use of several statistical techniques for between- and within-drug group comparisons revealed that pimozide and fluphenazine were equally effective in maintaining control of symptomatology of chronic schizophrenics at a level commensurate with or better than that provided by their previous medication. Side effects were characteristic of marketed neuroleptics, similar in severity and occurrence between study-drug groups, mainly extrapyramidal symptoms, and readily controlled with antiparkinsonian medication. Pimozide, slightly more potent than fluphenazine, proved to be equally effective for the long-term management of chronic schizophrenic patients.