PURPOSE: This study examines the response to treatment in 17 patients with kleptomania who were treated with naltrexone as monotherapy for up to 3 years. METHODS: Patients were treated with naltrexone (range, 50-200 mg/day) and were assessed at each clinic visit for stealing behavior, urges to steal, and for overall symptom severity. Liver function tests were examined regularly during treatment. RESULTS: Comparison of baseline symptoms with the most recent follow-up visit showed that 13 patients (76.5%) reported reduction in their urges to steal, and 7 (41.1%) reported no stealing behavior. In addition, 9 (52.9%) were rated as being either "not ill at all" or having "very mild" kleptomania symptoms at the most recent clinic visit. The mean effective dose of naltrexone was 135.3 +/- 38.6 mg/day. Monthly liver function tests revealed no elevations or abnormalities. CONCLUSION: These findings from a clinical setting suggest that a substantial percentage of patients report clinically significant improvement in kleptomania symptoms when treated with naltrexone.