To assess which membrane properties are modulated by the action of food restriction, characteristics of liver membrane structures of ad libitum-fed and food restricted Fischer 344 rats were analyzed over a wide age range. The results show that the yields of mitochondrial and microsomal membranes decreased in ad libitum-fed rats, but this age-related loss did not occur in food restricted rats until 30 months. Changes in membrane fatty acid composition which occurred with age were substantially modified by food restriction. Linoleic acid content progressively decreased in the membranes of ad libitum-fed rats with a concomitant increase of docosapentaenoic acid while an opposite pattern of change occurred in food restricted rats. Furthermore, food restriction maintained a low docosahexaenoic acid level in microsomes at all ages studied. While serum tocopherol increased markedly with age, there was little change in membrane tocopherol content in ad libitum-fed rats.