This comprehensive study investigated both the role of antidepressant drugs in the treatment of affective disorders of later life and their safety with careful clinical and pharmacological monitoring. A 7-week double-blind comparison was made of the efficacy and safety of nortriptyline (a tricyclic), phenelzine (a monoamine oxidase inhibitor), and placebo. The results indicated a response rate of approximately 60% for both nortriptyline and phenelzine versus a 13% response rate for placebo. Anticholinergic side effects were more frequently reported in the nortriptyline group. Orthostatic symptoms were reported with similar frequency in both drug groups. Overall, both drugs were well tolerated.