BP II MDE patients are treated initially with fluoxetine for 10 weeks. Patients who recover from MDE are then randomized to receive a relapse-prevention treatment of fluoxetine, lithium, a combination of fluoxetine and lithium, or placebo for 1 year. Patients undergo clinical and laboratory evaluations, including physical examinations, bloodwork, thyroid function tests, electrocardiogram (ECG), urinalysis, and HAM-D, YMR, CGI-S, CGI-I, and adverse events scales.