This pilot study compared the efficacy of orlistat as an adjunctive treatment for obesity between African American and Caucasian adolescents. Twenty obese adolescents with obesity-related co-morbid conditions underwent measurements of body composition, glucose homeostasis by frequently sampled intravenous glucose tolerance test (FSIGT), and fasting lipids before and after 6 months treatment with orlistat 120 mg tid in conjunction with a comprehensive behavioral program. Weight (p < 0.05), BMI (p < 0.001), total cholesterol (p < 0.001), LDL cholesterol (p < 0.001), fasting insulin (p < 0.02) and fasting glucose (p < 0.003) were lower after treatment. Insulin sensitivity, measured during the FSIGT, improved significantly (p < 0.02), as did fasting indices such as the homeostasis model assessment for insulin resistance (p < 0.01). African American subjects exhibited significantly less improvement in weight (p < 0.05), BMI (p < 0.01), waist circumference (p = 0.03), and insulin sensitivity (p = 0.05). Improvements in cholesterol were not significantly different between African Americans and Caucasians. We conclude that Caucasians lost more weight and had greater improvements in insulin sensitivity than African Americans, but both exhibited improvements in plasma lipids. The true benefit of orlistat treatment over a comprehensive behavioral program remains to be determined in placebo-controlled trials.