The results with a new monoamine oxidase inhibitor (a-methyl-benzylhydrazine) on 20 depressed patients are reported. The doses used orally ranged from 10 to 20 mg/day, during 20 to 90 days. The evalutation was made on the basis of clinical analytic observation. The results were as follow: very good improvement in 5 cases; 7 cases with good results; 4 cases with moderate improvement; 4 cases remained unchanged. The best results were observed in patients with reactive depression. Good results were observed in involutional and neurotic depressions. The symptomatic depressions arisig in the course of various psychoses were hardly, or not at all, influenced by the drug. Severe side effects were not present, except transitory jaundice observed in one case. The authors concluded that a-methyl-benzylhydrazine is a useful antidepressant drug in the treitment of depression, specially in reactive psychoses.