The dose-dependent hepatic hypertrophy and lipid accumulation, caused by dietary mirex, is associated with alteration of ratios of various components of simple lipid and phospholipid in rat liver. The concentration of diacylglycerol (which amounts to about 70% of the simple lipid), phosphatidylcholine (which amounts to about half of the phospholipid), and fatty acids decreased in lipid of the liver of mirex-treated rats (15,000 ppm for 3 days). The decreases accompanied concomitant increases in triacylglycerol, monoacylglycerol, and cholesteryl esters in simple lipid, and phosphatidylethanolamine and phosphatidylserine in phospholipid. Analyses of fatty acids of the components indicated an overall decrease in saturated acids and an increase in unsaturated arachidonic acid in both simple and phospholipid, as well as an increase in palmitoleic in simple lipid of livers of mirex-treated rats (15,000 ppm for 3 days). The changes in relative proportions and acyl composition of hepatic lipid by this toxic dose of mirex indicate that structural and functional integrity of hypertrophied hepatocytes may be compromised in mirex-treated rats.