Alimentary hypercholesterolemia acting over a sufficient period of time (in rabbits with all organs intact, 110 days or longer) causes deposition of cholesterol within the intima of the aorta. Deposition of cholesterol within the intima of the aorta initiates the formation of experimental atheromata. Thyroidectomy, splenectomy, and gonadectomy augment hypercholesterolemia and thereby facilitate and accelerate the development of experimental atheromata of the aorta in rabbits. Sublethal suprarenal insufficiency does not increase the susceptibility of rabbits to the development of such atheromata.