Summary: The lesions of atherosclerosis are proliferative smooth-muscle lesions which may result from various forms of endothelial injury or dysfunction associated with the different risk factors for atherosclerosis. These lesions have been associated with interactions between platelets, macrophages, and with substances released from these cells, including growth factors. Approaches toward lesion prevention should include: protection of the endothelium, particularly in relation to maintenance of its nonthrombogenic character: inhibition of platelet interactions; and understanding of the nature of growth factors that may be involved to permit development of approaches to prevent growth-factor activity, including binding of growth factors derived from platelets and macrophages upon other cells, in particular, smooth muscle.