This study involves adding allopurinol to subjects' current bipolar medications. This study will be a open label, naturalistic study. The subject will be examined monthly for manic symptoms for 2 years. Semi-structured interviews and study questionnaires will be administered to subjects at each visit. Monthly Follow-up Study Visits (once per month for 2 years - Months 1-5, 7-11, 13-17, 19-23) may be conducted either in-person or over the phone. All of the questionnaires will be administered by a clinician if the visit is completed over the phone. However, the 6-month interval visits (Months 6, 12, 18, and 24) must be done at the research center.