A dismantling strategy was used to assess the effects of therapist participation and group contact in the behavioral treatment of obesity. A Standard Behavioral Treatment including group contact and therapist leadership was compared with a Taped Behavioral Treatment conducted in groups via audiotape without a therapist, a Bibliotherapy treatment lacking both group contact and a therapist, and a nonbehavioral Insight group conducted by a therapist. All treatments resulted in statistically significant weight loss. The Standard Behavioral Treatment was superior to the other three treatments on one of the outcome measures. The role of the therapist in maintaining participants' motivation to implement the behavioral techniques presented in treatment is discussed.