['The combination of vitamin E with aspirin is becoming an attractive therapeutic approach to prevent thrombotic vascular accidents. In this study we investigated the capacity of vitamin E (50 and 100 M) to enhance the antiplatelet effect of aspirin.', 'The dose-response curves of platelet aggregation, dense body secretion, phospholipase C activation and calcium mobilization were measured in aspirin-treated platelets with and without added vitamin E (50 and 100 M). The role of vitamin E in reducing platelet adhesion to collagen was also studied.', 'We demonstrated that, in platelets incubated with 100 M vitamin E, collagen-concentration ( g/mL) able to induce 50% of the maximal platelet aggregation and of the calcium mobilization was higher than in controls (11.6 versus 3.8 and 21.3 versus 9.8, respectively). Furthermore, 50 M vitamin E reduced platelet adhesion to collagen by about 80%.'] Does vitamin E potentiate the antiplatelet activity of aspirin in collagen-stimulated platelets?