Intimal calcific atherosclerosis may lead to diminished organ perfusion, whereas medial calcification (Mönckeberg type) is of no physiologic significance. Thirty-nine excised arteries were studied by correlating specimen radiographs with transverse histologic sections to determine whether intimal and medial calcification could be reliably distinguished by radiographic criteria. The calcification was correctly localized in 92% of the arteries studied. Intimal calcification was usually irregular and patchy, whereas medial calcification was regular and diffuse. In one case, extensive medial calcification obscured intimal disease. Plain radiographs may be a useful way to follow progression, regression and the effects of therapy on vaso-occlusive disease in certain high-risk patients.