Comorbidity was studied in 41 manic and mixed-state bipolar patients at first hospitalization. The lifetime prevalence of comorbidity was high; 21 subjects (51.2%) had at least one other psychiatric diagnosis (N = 16, 39.0%) or medical disorder (N = 9, 22.0%). Nine subjects had multiple comorbid diagnoses. Women were 2.7 times more likely to have a comorbid diagnosis. The presence of comorbidity was not associated with differences in outcome measures.