We are conducting a two year longitudinal study of mood disorders in a group of 103 stroke patients. During the first six month period following the stroke the prevalence of symptoms of major depression increased from 23 per cent to 34 per cent while the frequency of symptoms of dysthymic depression increased from 20 per cent to 26 per cent. In addition, 10 of 13 patients who had major depresssive symptoms during the initial evaluation continued to have these symptoms at six months follow-up and 4 of 9 patients who had minor depression in hospital developed major depression, while 5 of 9 continued to have minor depressive symptoms. Thus, the duration of depression following stroke is more than six months and the prevalence of major depressive symptoms increases steadily for the first half year after a cerebral hemorrhage or ischemic lesion.