Therapeutic efficacy and target symptoms with clocapramine were compared with those with haloperidol by the crossover method, in a total of 26 chronic schizophrenic patients, by administration of one of the drugs for the first 14 weeks and the other for the next 14 weeks. The final global improvement rating showed no significant difference between the two groups, but clocapramine administered as first drug appeared to have a more pronounced effect than haloperidol. According to the improvement rate in psychotic symptoms, clocapramine tended to be superior to haloperidol for motor retardation, scanty speech and disturbance of thought. In addition the frequency of side-effects was lower with clocapramine than with haloperidol. Neither the side-effects nor abnormal laboratory test results were severe enough to terminate the trial. Clocapramine is considered to be equivalent or superior to haloperidol in terms of anti-psychotic effect in chronic schizophrenia, and is relatively safer than haloperidol.