LTHOUGH the subject of many earlier investigations in both humans and experimental animals, the exact role of the gonadal system in the atherogenic process and cholesterol metabolism is obscure (1, 2). Recent work from this laboratory has shown a striking sex associated resistance to hypercholesteremia among rabbits (3). Males were found to have lower serum cholesterol levels than females. Furthermore, males, as a group, also demonstrated a lower cholesteremic response to a discriminating dose of dietary cholesterol. This sex difference among rabbits was shown to be related closely to the production of the gonadal hormones.Microscopic arterial lesions have been induced in the rat by a variety of techniques (4–8). Rats that had been fed diets containing cholesterol and sodium cholate demonstrated grossly visible atheromatous plaques which, upon microscopic observation, revealed foam cells and intracellular lipid infiltration of both the intima and media (8, 9).