 Patients between 18 and 70 years of age with bipolar I or II disorder without psychosis may be eligible for this 8-week study. Candidates must be currently depressed, must have had at least one previous major depressive episode, and must have failed to improve with prior treatment with at least one antidepressant. They will be screened with a medical history, physical examination, electrocardiogram EKG, blood and urine tests, and psychiatric evaluation. A blood or urine sample will be analyzed for illegal drugs. Women of childbearing potential will have a pregnancy test. 