Weight gain represents a frequent side effect of antipsychotic drug treatment. The current trial investigated the effect of add-on treatment with sibutramine in schizophrenia outpatients who had gained more than 7% of weight during the course of treatment. This 24-week placebo-controlled study evaluated the effects of sibutramine added to ongoing antipsychotic treatment. Weight, waist–hip ratio, BMI, blood pressure/pulse and ECG were monitored regularly. In addition, several laboratory tests were performed. Psychopathological symptoms and side effects were assessed frequently. Fifteen patients were assigned randomly to add-on treatment with sibutramine 10 mg or placebo. The two groups did not differ in weight, sociodemographic, or clinical data. Eleven patients were considered for statistical analysis. Significant weight loss was observed in the sibutramine group (mean=−6.1 kg), whereas patients on placebo experienced a mean weight gain of 1.9 kg. A reduction in HbA1c was apparent in the sibutramine but not in the placebo group. No significant between-group differences were found in changes in psychopathology or drug safety. This pilot trial suggests that adjunctive treatment with sibutramine may be safe and effective in schizophrenic patients with antipsychotic-induced weight gain.