The behavior of five supervisors, 19 trainee family therapists, and 20 clients before, during, and after 88 live supervisory phone-in events was examined in this study to determine the correlates of client cooperation. Following supervisory phone-in conversations, client cooperation was associated exclusively with the presence and quality of the collaborative behavior shown by the therapist. Isomorphism between the behavior of the supervisor and therapist was not associated with subsequent client cooperation, nor was any particular category of supervisor behavior. Surprisingly, isomorphism between the quality of supervisor and therapist behavior preceded those events where client resistance occurred.