To determine whether combined therapy with the lipid lowering agents colestipol hydrochloride plus niacin would produce significant change in coronary, carotid, and femoral artery atherosclerosis and coronary bypass graft lesions as determined by angiography. Also, to determine possible correlations between lesion changes and plasma lipid and lipoprotein cholesterol levels and to explore interrelationships of atherosclerosis change in femoral, coronary, and carotid arteries.