The influence of depression on the long-term outcome of stroke patients was examined among 390 of 486 consecutive patients aged 55-85 years. They completed, at 3 months after ischaemic stroke, a detailed medical, neurological, and radiological stroke evaluation, structured measures of emotion (Beck's Depression Inventory, BDI), handicap (Rankin scale, RS), and assessment of activities of daily living (Barthel Index, BI). Further RS and BI was evaluated at 15-month follow-up from these 390 patients and BDI in 276 patients. A group of 256 patients completed, in addition to the 15-month follow-up, a comprehensive psychiatric evaluation, including the Present State Examination 3 months after stroke. The DSM-III-R criteria were used for diagnosis of the depressive disorders. BDI identified depression (cut-off point > or = 10 for depression) in 171 (43.9%) of 390 and in 123 (44.6%) of 276 patients at 3- and 15-month follow-up. DSM-III-R major depression was diagnosed in 66 (25.8%), and minor depression in 32 (12.5%), of 256 patients 3 months after stroke. Patients with BDI > or = 10, or major, but not minor, depression more often had poor functional outcome (RS > II and BI < 17) at 15 months. Poor functional outcome at 3 months also correlated with depression at 15 months. In logistic regression analysis, depression at 3 months (Beck > or = 10) correlated with poor functional outcome at 15 months (RS > II) (OR 2.5, 95% CI 1.6-3.8). More careful examination and treatment of depression in stroke patients is emphasized.