Epidemiologic data as well as data from treatmentseeking populations indicate that substance abuse disorders and other psychiatric disorders co-occur more commonly than would be expected by chance. In particular, substance abuse, especially cocaine abuse or dependence and alcoholism, is a far more common phenomenon in the population of patients with bipolar affective disorder than in the general population. National Institute of Mental Health Epidemiologic Catchment Area data indicate that bipolar affective disorder is the axis I disorder most likely to be associated with some form of substance abuse or dependence. Evidence from patient samples seeking treatment for substance abuse disorders as well as for psychiatric disorders suggests that clinical samples reflect similar patterns. There is evidence that bipolar patients with substance abuse have a worse course of illness. Diagnosing bipolar affective disorder in the face of substance abuse is difficult because the effects of drugs of abuse, particularly with chronic use, can mimic nearly any psychiatric disorder. At present, the data concerning a genetic link between bipolar affective disorder and substance abuse disorders are inconclusive. There are very few controlled data addressing either clinical features of, or specific treatment efforts with, this population. There is some theoretic rationale for the use of anticonvulsant, antikindling agents in this population, but no controlled studies have as yet been reported. In particular, a comparison of a moodstabilizing agent, such as lithium, with an antikindling agent, such as valproate or carbamazepine, would be of theoretic and practical interest.