The relationship of lipoperoxidemia and HDL-cholesterolemia to circulating zinc and copper was investigated in patients undergoing chronic hemodialysis. When the serum zinc level was low and the copper level was high, or when the zinc, copper ratio was low, decreased concentrations of HDL-cholesterol were observed. In view of the high incidence of atherosclerosis among patients undergoing chronic hemodialysis, zinc and copper may somehow contribute to atherogenesis by affecting the serum HDL-cholesterol concentrations.