The effects of tocotrienol-rich vitamin E from palm oil on serum vitamin E concentrations, serum lipids, plasma prostaglandins and platelet function (assessed by bleeding time and aggregation) were investigated in 44 subjects (23 males, 21 females) with hypercholesterolaemia. Following a 6-week run-in period, subjects were randomized for 20 weeks to receive either tocotrienol or placebo (superolein from palm oil), in increasing dosages. By the 4th week of supplementation, and at lowest dosages, there were significant increases in serum concentrations of total vitamin E, total tocopherol, and total tocotrienol in the active, but not placebo group, and these persisted in the highest dosage group for 16 weeks. At no stage during the study were there any significant changes in serum lipids (total cholesterol, HDL cholesterol, LDL cholesterol or triglycerides), or any changes in lipids predictable by serum vitamin E status itself, even when body composition was taken into account. There were also no changes in plasma prostaglandins or in platelet function. Evidence was obtained that the serum responses to ingested tocotrienols and tocopherols favoured tocopherol over tocotrienol, and alpha tocopherol over gamma tocopherol.