Alcohol and substance use disorders are more common in bipolar disorder bipolar disorder than in any other DSM-IV (Diagnostic and Statistical Manual of Mental Disorders) Axis I disorder, estimated to occur in up to 60% of patients with bipolar disorder. Alcohol use is associated with poor outcome in bipolar disorder, and yet these co-occurring conditions are understudied. To date, there is only one published placebo-controlled trial of an agent for the treatment of alcohol dependence alcohol dependence in bipolar disorder. The purpose of the proposed study is to evaluate the efficacy of a topiramate as a treatment for alcohol dependence in patients with bipolar disorder. This is a 12-week, randomized, placebo-controlled study of the efficacy of topiramate adjunctive to standard treatment for bipolar disorder in patients with alcohol dependence and bipolar disorder. Additional aims of the study are to document the safety and tolerability of topiramate in this population, and to evaluate to effect of decreased drinking on mood symptoms. The study involves the enrollment of a total of 80 patients with co-occurring alcohol dependence and bipolar disorder over the course of 40 months at the Massachusetts General Hospital (MGH) Bipolar Clinic and Research Program (BCRP) (www.manicdepressive.org). With a conservative estimate of a 30% dropout rate, approximately 56 of the 80 patients with these two comorbid conditions will complete 12 weeks treatment with either topiramate or placebo.