Thirty chronic ambulatory schizophrenic patients whose main psychopathology was characterized by the persistence of negative symptoms, such as emotional withdrawal, depressed mood, motor retardation and blunted affect were included in this project in order to evaluate the therapeutic efficacy of tranylcypromine plus chlorpromazine therapy. The results show that tranylcypromine when added to the usual dose of chlorpromazine, in many instances, induces a definite improvement in these patients' clinical condition, that such treatment is safe and it may be also useful in preventing the occurrence of extra-pyramidal symptoms.