The therapeutic alliance is considered as one of the active relational factors to improve the outcome of patients engaged in a psychotherapeutic process. Our objective was to examine the role played by the therapeutic alliance in psychodynamic versus supportive psychotherapy. We examined data from a previously published randomized controlled study. Outpatients suffering from depression (n=74) received the same antidepressant (clomipramine) and were randomized into two groups, receiving either psychodynamic or supportive psychotherapy. Subjects were assessed at inclusion (Structured Clinical Interview for DSM-IV Disorders, SCID), during treatment and at discharge (Global Assessment Scale, Hamilton Depression Rating Scale, Helping Alliance questionnaire). Over time, the therapeutic alliance improved regardless of condition, and the relationship between alliance and outcome strengthened. This relationship was significant only among patients assigned to the supportive therapy condition. These data suggest that although the therapeutic alliance is an important factor in psychodynamic treatment, additional ingredients may be involved in its superiority compared to supportive therapy.