Rats were fed vitamin E at various dietary concentrations providing dosages of up to 2000 mg/kg bodyweight/day for 104 weeks. Vitamin K supplementation suppressed the induced hypoprothrombinaemia. Growth rate and survival were unaltered by treatment, and, apart from a trend towards fewer mammary tumours in females, the tumour profile was unaffected. Changes in serum liver enzyme activity and in the appearance of the hepatic macrophages suggested a limited hepatic response to vitamin E overload.