The effect of vitamin E on platelet function has been reviewed. Although vitamin E inhibits platelet aggregation in vitro, in vivo it has no significant effect when administered in doses up to 1200 U/day. Platelet adhesion, on the contrary, is strongly inhibited by alpha-tocopherol. Doses of 400 IU/day provide greater than 75% inhibition of platelet adhesion to a variety of adhesive proteins when tested at low shear rate in a laminar flow chamber. The antiadhesive effect of vitamin E appears to be related to a reduction in the number and size of pseudopodia upon platelet activation. This effect of vitamin E may be related to changes in fatty acylation of structural platelet proteins. Clinical studies of vitamin E supplementation in patients with thromboembolic disease are in progress.