Combination Therapy in Dual Diagnosis Bipolar Rapid Cycling: This study recruits males and females age 18 and older who currently meet diagnostic criteria for rapid cycling bipolar disorder (type I or II) and who have met the criteria for substance abuse or dependence of cocaine, marijuana and/or alcohol within the past six months. Patients begin treatment with a combination of lithium and divalproex. Once these medications are tolerated, they are randomly assigned to double-blind treatment with lamotrigine or placebo. Patients remain in this study until they experience a marked bimodal response for four consecutive weeks. This study is sponsored by the Stanley Foundation.