In a 6 month prospective study of 232 patients with cerebral ischaemia, 100 (43%) had a prior history of heart disease. In 22 of the patients with prior heart disease an unsuspected cardiac disorder was subsequently detected (6 atrial fibrillation, 13 cardiomegaly or left ventricular hypertrophy and 3 ischaemic heart disease). In patients without prior heart disease, 47 (20%) were found to have cardiac disease: 6 atrial fibrillation, 31 cardiomegaly or left ventricular hypertrophy 9 ischaemic heart disease and 1 left bundle branch block. Previously unsuspected or asymptomatic cardiac disease is common in patients with cerebral ischaemia.