BACKGROUND The efficacy of treatments for pediatric obesity remains unclear. OBJECTIVE We performed a systematic review of randomized trials to estimate the efficacy of nonsurgical interventions for pediatric obesity. METHODS Librarian-designed search strategies of nine electronic databases from inception until February 2006, review of reference lists from published reviews, and content expert advice provided potentially eligible studies. METHODS Eligible studies were randomized trials of overweight children and adolescents assessing the effect of nonsurgical interventions on obesity outcomes. METHODS Independently and in duplicate, reviewers assessed the quality of each trial and collected data on interventions and outcomes. RESULTS Of 76 eligible trials, 61 had complete data for meta-analysis. Short-term medications were effective, including sibutramine [random-effects pooled estimate of body mass index (BMI) loss of 2.4 kg/m(2) with a 95% confidence interval (CI) of 1.8-3.1; proportion of between-study inconsistency not due to chance (I(2)) = 30%] and orlistat (BMI loss = 0.7 kg/m(2); CI = 0.3-1.2; I(2) = 0%). Trials that measured the effect of physical activity on adiposity (i.e. percent body fat and fat-free mass) found a moderate treatment effect (effect size = -0.52; CI = -0.73 to -0.30; I(2) = 0%), whereas trials measuring the effect on BMI found no significant effect (effect size = -0.02; CI = -0.21 to 0.18; I(2) = 0%), but reporting bias may explain this finding. Combined lifestyle interventions (24 trials) led to small changes in BMI. CONCLUSIONS Limited evidence supports the short-term efficacy of medications and lifestyle interventions. The long-term efficacy and safety of pediatric obesity treatments remain unclear.