Young guinea pigs were fed a purified diet containing vitamin E for 3 weeks and then fed the diet without vitamin E for 8 weeks. Levels of vitamin E in plasma and liver decreased to low values within a week. Depletion rates for heart and muscle were much slower, whereas the rate of loss from fat was negligible. In experiments with more mature guinea pigs and a depletion period of 4 months, the depletion rate of tocopherol from fat was also barely detectable. Both yound and mature guinea pigs developed myopathy after 8 weeks of depletion. Apparently, tocopherol in adipose tissue is not sufficiently available to maintain plasma tocopherol levels or to prevent signs of vitamin E deficiency. Even during fasting, adipose tissue tocopherol was not mobilized readily. During a 4 day fast, adipose tissue mass diminished considerably, but there was no appreciable loss of tocopherol.