Familial hypercholesterolemia is an autosomal co-dominant disorder resulting in abnormal LDL receptor function, profoundly elevated concentrations of low density lipoproteins, accelerated atherosclerosis and death by early adulthood. This disease is heterogeneous in both the degree of LDL receptor dysfunction as well as the age of death. Liver transplantation has been demonstrated to virtually normalize plasma lipoprotein concentrations in homozygous FH and the recent cloning of a functional LDL receptor gene holds promise in the definitive treatment of this condition. We propose performing longitudinal sequential cardiologic studies utilizing noninvasive techniques in homozygous patients with well-characterized LDL receptor defects. Sequential cardiovascular study of these patients will not only characterize the progression of atherosclerosis heart disease in this disease, it may also permit the identification of individuals with would be likely to benefit from liver transplantation and/or genetic engineering.