This study examined the comorbid diagnosis of a sample of bipolar II patients, comparing patients with comorbidity & those with pure bipolar II disorder. 40 patients were assessed. Only the rates of suicidal ideation & suicide attempts were significantly different between patients with & without comorbidity. Although the rates of comorbidity are relatively high in bipolar II disorder, most clinical & course variables are strikingly similar in patients with & without comorbidity except for suicidal behaviour, suggesting that comorbidity does not reduce the validity of diagnosis of bipolar II disorder. (34 refs.)