We administered high-dose vitamin E to healthy adult male volunteers and assessed the safety of such supplementation. Fourteen volunteers received daily 1,200 IU of vitamin E (800 mg of D-alpha-tocopherol) for 28 d and eight controls were also enrolled. The volunteers treated with vitamin E showed no abnormalities during the study period. The alpha-tocopherol concentrations of plasma and platelets were markedly elevated by vitamin E treatment, but there were no significant differences in platelet aggregation, coagulation, and the clinical parameters between the two groups. In conclusion, a high dose of vitamin E for 28 d had no adverse effects in healthy men.