In a controlled outcome study of phobias, 111 adult patients (69% women, 31% men) received a course of 26 weekly treatment sessions consisting of (1) behavior therapy and imipramine hydrochloride (2) behavior therapy and placebo, or (3) supportive psychotherapy and imipramine. Patients were classified as agoraphobic, mixed phobic, or simple phobic. The great majority of patients in all groups showed moderate to marked global improvement (70% to 86%, depending on rater). In agoraphobics and mixed phobics (both groups experiencing spontaneous panic attacks), imipramine was significantly superior to placebo. There was no difference between behavior therapy and supportive therapy, both resulting in high improvement rates (76% to 100%, depending on rater). In simple phobic patients, there was a high rate of improvement with all treatment regimens (72% to 93%, depending on rater), with no significant difference between imipramine and placebo or between behavior therapy and supportive therapy. Of 88 moderately to markedly improved patients followed up for one year after completing treatment, 83% maintained their gains and 17% relapsed. No patients showed symptom substitution. Eighteen percent of the patients receiving imipramine hydrochloride showed marked stimulant side effects on from 5 to 75 mg/day.