Effect of dietary levels of essential fatty acid (EFA), 20 % corn oil, 5 % corn oil, 20 % lard and no fat, on the overnight fasting-induced changes in the concentration and composition of liver lipids of rats was investigated. The increase due to fasting in triglyceride (TG) was not observed when the liver previously contained relatively large amounts of the glyceride. In contrast, phospholipid levels were similarly and significantly increased. Overnight fasting induced increases in percentage of linoleic acid in TG and arachidonic acid in phosphatidylcholine, the extents of those being nearly paralleled with decreasing dietary levels of EFA. These changes are interpreted as a reflection of the compensatory action of the body.