In order to quantify the accumulation of apoprotein B in skin we determined the amount of apo B in the skin of atherosclerotic patients using a modified Hoff's method with extraction and electroimmunoassay. Skin biopsies were taken from the lower limbs of nineteen male patients with arteriosclerosis obliterans during revascularization and from the thoracic region of thirty male patients with ischemic heart disease during coronary bypass graft surgery and thirty one male patients with abnormalities of cardiac valves during valvuloplasty. A significant positive correlation between skin apo B and skin cholesterol was found in three groups. Our data support the hypothesis that cholesterol deposit in the skin of patients with atherosclerosis is derived from plasma lipoprotein B and that the content of skin lipids parallels with the development of atherosclerosis in man.