OBJECTIVE: To report observations on the efficacy and tolerability of topiramate in a sample of five patients with severe symptoms of bulimia nervosa and comorbid mood and/or anxiety disorders. METHOD: Topiramate was added to other psychotropic medication under open-label conditions up to the maximum tolerated dose or until remission of the eating disorder was achieved. RESULTS: Topiramate almost completely eliminated binging and purging behavior in three of the five patients. Improvement was maintained throughout the period of follow-up for up to 18 months. One patient showed a partial, temporary response, and the fifth was intolerant of the drug and unable to complete an adequate trial. DISCUSSION: These results suggest strongly that the efficacy of topiramate in patients with bulimia nervosa with and without comorbid mood and anxiety disorders should be investigated more fully. Copyright 2003 by Wiley Periodicals, Inc.