This interview study was conducted to explore the onset, course, and features of bipolar affective disorder complicated by substance abuse. Forty-four patients with a diagnosis of bipolar affective disorder were interviewed using the Structured Clinical Interview for DSM-III-R, Hamilton Rating Scale for Depression, Young Mania Rating Scale, and a questionnaire concerning psychiatric history. Current substance users averaged twice as many hospitalizations for mood problems. The age of onset of mood problems for substance users was significantly earlier than that of the nonusers (p < or = .05). Substance users were four times as likely to have other comorbid axis I disorders (p < or = .05) and twice as likely to have dysphoric mania at time of interview. This preliminary study suggests that individuals with bipolar affective disorder complicated by substance abuse may have more hospitalizations, a higher incidence of dysphoric mania, earlier onset of mood problems, and more comorbid axis I disorders.