In patients dying in adolescence with familial hypercholesterolemia a combination of xanthomata of the skin and tendons, atheromatous plaques on the aortic and mitral valves, the coronary artery outlets and in the proximal aorta is frequently found. However, little is known of the sequence of these changes or their clinical equivalents. For this reason findings are described in two patients whose homozygous familial hypercholesterolemia is confirmed by studies of the cell biochemistry of the dermal fibroblasts after an observation period of eight and twelve years.