Thromboembolism, increased platelet aggregation and high plasma concentration of beta-thromboglobulin were observed frequently in hemizygotes and heterozygotes of Fabry's disease. The administration of vitamin E and ticlopidine could improve the increased platelet aggregation in this disease. The platelet activation, probably induced by vascular endothelial damages, would accelerate atherosclerotic and thromboembolic vascular changes. Antiplatelet therapy will be effective for the prevention of these vascular complications in this disease.