Sixty elderly depressed patients who had responded to either nortriptyline hydrochloride or phenelzine sulfate were followed up under double-blind conditions during four to eight months of continuation treatment. Over 70% of patients (43) remained well during this period, while 11 (18.3%) had relapses, three (5.0%) dropped out because of side effects, and three (5.0%) prematurely terminated in good clinical condition. There was no significant difference in the relapse rate between patients receiving nortriptyline (five [16.7%]) and those receiving phenelzine (six [20.0%]). Patients receiving phenelzine were more likely to require dose reductions, and all three patients who dropped out because of side effects were receiving phenelzine. Patients with chronic depression (greater than two years' duration) accounted for all of the relapses.