The authors describe 9 patients with bipolar affective disorder associated with cerebrovascular lesions. Eight had negative family histories of affective disorders and late age at onset (after age 40) of manic-depressive symptoms. Only one, with positive family history of affective disorders, developed mood swings before age 40. Clinical subtypes of bipolar disorder and patterns of affective cycling in these stroke patients resembled those previously reported in functional bipolar disorder. Five patients had concurrent hyperkinetic movement disorders, and one depressed patient presented with unilateral left-sided parkinsonism that disappeared during a manic switch. In most patients, bipolar affective disorder was associated with right hemisphere lesions that involved subcortical and midline structures. Findings suggest that damage to frontal-basal ganglia-thalamocortical circuits by subcortical vascular lesions may simultaneously provoke disorders of movement and mood regulation.