As a species the mouse is highly resistant to atherosclerosis. However, through induced mutations it has been possible to develop lines of mice that are susceptible to this disease. For example, mice that are deficient in apolipoprotein E, a ligand important in lipoprotein clearance, develop atherosclerotic lesions resembling those observed in humans. These lesions are exacerbated when the mice are fed a high-cholesterol, high-fat, Western-type diet. Other promising models are mice that are deficient in the low density lipoprotein receptor and transgenic mice that express human apolipoprotein B and transdominant mutant forms of apolipoprotein E. These models are now being used to study the pathogenesis of atherosclerotic lesions, as well as the influence of genetics, environment, hormones, and drugs on lesion development.