Adolescent obesity is becoming a health problem in both developed and developing countries. Antiobesity drug therapy is not currently indicated for the treatment of adolescent obesity and remains investigational at this time. The aim of this study was to determine the efficacy and safety of sibutramine in obese adolescents. A randomized, double-blind, placebo-controlled trial, enrolling 60 adolescents, aged 14-17 yr, for 6 months was conducted. In the first month, all patients received placebo and a hypocaloric diet plus exercise orientation. For the next 6 months, participants received either sibutramine or placebo. Patients assigned to sibutramine group lost an average of 10.3 +/- 6.6 kg, and patients in placebo group lost 2.4 +/- 2.5 kg (P < 0.001). The mean body mass index reduction was significantly greater in the sibutramine group (3.6 +/- 2.5 kg/m(2)) than in the placebo group (0.9 +/- 0.9 kg/m(2); P < 0.001). No participant withdrew because of adverse events, and no difference in blood pressure or heart rate was noted between groups. There were no changes in echocardiographic parameters. In conclusion, sibutramine plus diet and exercise induced significantly more weight loss in obese adolescents.