Occlusion, reocclusion, and/or restenosis after interventions can be due to four mechanisms which require different approaches: 1) mechanical problems should be prevented by careful surgery and PTCA; 2) early platelet aggregation and thrombosis can be reduced by acetylsalicylic acid; 3) fibrocellular hyperplasia leading to restenosis after PTCA. So far prevention has been unsuccessful; and 4) progression of coronary disease, which may be prevented or delayed by rigorous reduction of risk factors and lipid lowering drugs, while again, acetylsalicylic acid may prevent late platelet aggregation and infarction.