Clozapine therapy for 2,996 patients with treatment-refractory schizophrenia was examined over a five-year period in the Veterans Affairs health care system. Patients were assessed with the Brief Psychiatric Rating Scale (BPRS) and the Abnormal Involuntary Movement Scale (AIMS). BPRS scores, which were available for 522 patients, indicated a significant improvement, as did AIMS scores, which were available for 252 patients. Compared with individuals who showed a modest improvement, those with a more robust response to clozapine had higher initial BPRS scores and were three times more likely to have been suicidal in the month before starting clozapine therapy.