We determined the fatty acid composition of the lipids of cynomolgus monkey retina in animals fed commercial chow or a saturated fat, cholesterol-enriched atherogenic diet for 100 days. Doxosahexaenoic acid (22 : 6) accounted for 25.8% of the ethanolamine phosphoglyceride fatty acids, 17.6% of the serine plus inositol phosphoglyceride fatty acids, 8.4% of the choline phosphoglyceride fatty acids and 5.8% of the neutral lipid fatty acids in the retinas of the chow-fed animals. Therefore, monkey retinas, like those of other mammalian species, ordinarily contain large amounts of 22 : 6. Retinas from the monkeys fed the atherogenic diet contained less 22 : 6 as well as other polyunsaturates in each of the phospholipid classes. The decrease in polyunsaturates was compensated for by increases in palmitic, stearic, and oleic acids. There was no difference in the amount of phospholipid, the distribution of phospholipid classes, or the amount of cholesterol in the retinas of the monkeys fed the atherogenic diet. These results indicate that the single type of lipid alteration produced in the retina by a diet enriched in saturated fat and cholesterol is a decrease in the polyunsaturation of the retinal phospholipids. The reduction in retinal 22 : 6 content might have significance for photoreceptor function.