Platelets play an important role in atherogenesis. This has given rise to the speculation that inhibitors of platelet function may prevent atherosclerotic changes. Two distinct therapeutic goals might be achieved by the use of inhibitors of platelet function in vascular disease - one, the prevention of thrombosis and, two, the prevention of atherosclerosis. The choice of inhibitor may well determine the goal achieved. Thus far, the data available indicate that inhibitors of platelet aggregation, such as aspirin, are the most effective in the prevention of thrombosis, while inhibitors of platelet adherence, such as dipyridamole, are likely to be the most effective in the prevention of atherosclerosis.