OBJECTIVE: In this study, we evaluated the efficacy of sibutramine in combination with hypoglycemic drugs in obese type 2 diabetic women whose glucose levels were poorly regulated. RESEARCH DESIGN AND METHODS: Female patients with type 2 diabetes, poorly controlled glucose levels, and HbA(1c) >8% were randomly assigned to one of two groups. In addition to their prescribed hypoglycemic agents (maximum doses of sulfonylureas and metformin), one group (n = 30) received a placebo twice daily for 6 months and the other (n = 30) received sibutramine 10 mg b.i.d. for the same period. RESULTS: One patient in the sibutramine group was excluded during the study period because of hypertension; thus, a total of 29 data sets were analyzed for this group. In the placebo group, five patients had to be excluded because of low treatment efficacy, leaving a total of 25 who completed the study. Comparing the changes that occurred over 6 months in the sibutramine and placebo groups, the former showed significantly greater reductions in fasting blood glucose (P < 0.0001), second-hour postprandial blood glucose (P < 0.0001), insulin resistance (P < 0.0001), waist circumference (P < 0.0001), BMI (P < 0.0001), HbA(1c) (P < 0.0001), diastolic blood pressure, pulse rate, uric acid levels, and all elements of the lipid profile except HDL cholesterol and apolipoprotein A1. CONCLUSIONS: The addition of sibutramine to oral hypoglycemic therapy resulted in significant weight loss and improvement in metabolic parameters in this patient group. Sibutramine is an effective adjunct to oral hypoglycemic therapy in obese women with type 2 diabetes.