The Watanabe heritable hyperlipidemic (WHHL) rabbit has proved to be an invaluable animal model of human familial hypercholesterolemia. Watanabe rabbits have a rare genetic defect. Total cholesterol levels can be eight to fourteen times higher in Watanabe rabbits than in normal rabbits. As a result, they develop vascular lesions, atherosclerotic disease, and sometimes heart attacks. The manifestation of atherosclerotic lesions in WHHL rabbits increases progressively with age but the presence of atherosclerotic lesions in newborn WHHL rabbits suggest that the process may commence in utero. This defect in rabbits is the equivalent of the described disease in humans.