By autoradiography it has been demonstrated that parenterally administered S35as sulfate is localized in the area of arterial plaque formation in rabbits with induced atherosclerosis. Dialysis of such tissue, after fat extraction to rid the tissue of inorganic sulfate, shows a much larger amount of sulfate remaining in the aortas of diseased animals as compared to controls suggesting that it is in combination with the mucopolysaccharides of the artery.