Objective: Since peers have such an important influence on adolescents, we evaluated the efficacy of adding peer-based 'adventure therapy' to a standard cognitive-behavioral weight control program for overweight adolescents. Methods: Adolescents (N ¼ 76) aged 13-16 years and 20 to 80% overweight (M ¼ 60.56%, s.d. ¼ 15.17%), were randomly assigned to one of two treatment conditions: cognitive-behavioral group treatment with 'adventure therapy' similar to Outward Bound s (cognitive-behavioral treatment with peer-enhanced adventure therapy (CBT þ PEAT)) or cognitive-behavioral group treatment with aerobic exercise (CBT þ EXER). Anthropometric and psychosocial measures were obtained at baseline, at the end of the 16-week intervention, and at 10 months following randomization. Results: Adolescents assigned to both treatment conditions demonstrated significant weight loss over time, F ¼ 29.06, df ¼ 2, 53, Po0.01. Average weight loss did not differ significantly between groups (À5.31 kg for CBT þ PEAT and À3.20 kg for CBT þ EXER) at the end of treatment. There was a significant difference in the percentage of participants maintaining a minimum 4.5 kg (10 pounds) weight loss (35% in the CBT þ PEAT condition vs 12% in the CBT þ EXER condition, P ¼ 0.042) 10 months from randomization. We also observed a significant age by treatment group interaction, such that older adolescents randomized to CBT þ PEAT demonstrated more than four times the weight loss of older adolescents assigned to CBT þ EXER (M ¼ À7.86 kg vs M ¼ À1.72 kg) at the end of treatment. Conclusions: Peer-based 'adventure therapy' is a promising adjunct to standard cognitive-behavioral weight control intervention for adolescents, and may be most effective for older adolescents.