The relationship between therapeutic alliance and treatment outcome was examined for depressed outpatients who received interpersonal psychotherapy, cognitive-behavior therapy, imipramine with clinical management, or placebo with clinical management. Clinical raters scored videotapes of early, middle, and late therapy sessions for 225 cases (619 sessions). Outcome was assessed from patients' and clinical evaluators' perspectives and from depressive symptomatology. Therapeutic alliance was found to have a significant effect on clinical outcome for both psychotherapies and for active and placebo pharmacotherapy. Ratings of patient contribution to the alliance were significantly related to treatment outcome; ratings of therapist contribution to the alliance and outcome were not significantly linked. These results indicate that the therapeutic alliance is a common factor with significant influence on outcome.