The incidence of stroke in the young is higher in the Indian subcontinent than in the West, but the precise cause is not known. Previous angiographic studies in cases of "young stroke" have yielded variable results. The present angiographic study of 143 cases of young stroke (under 40 years of age) showed a high incidence of abnormality (71%). The lesions included atherosclerotic disease of the internal carotid artery (68%), stenosis/occlusion of the major intracranial vessels (37%) and small-vessel disease. Tandem lesions were common (26%). Primary atherosclerosis is thought to be the cause of young stroke in the Indian population.