A prospective, uncontrolled clinical trial was conducted to test the safety and efficacy of intramuscular chlorpromazine (1 mg/kg) in the acute, outpatient treatment of migraine. One hundred adult patients were included in the study. There was complete relief of both pain and nausea/emesis symptoms in 96 patients within 55 minutes of the injection. Eighteen patients experienced orthostatic hypotension following injection. All but one responded to noninvasive therapy. The results suggest that chlorpromazine is a safe, effective alternative medication in the outpatient treatment of acute migraine.