BACKGROUND AND OBJECTIVES: The proximal left anterior descending artery (LAD) is one of the most important arterial segments due to its wide area of myocardial blood supply and the high incidence of restenosis after revascularization (RV) with percutaneous coronary intervention (PCI), especially in patients with LAD ostial and/or main involvement. SUBJECTS AND METHODS: One hundred and ninety four patients (58.9+/-10.9 year-old, 154 male) that had undergone PCI at proximal LAD lesions were divided into four lesion types; Type I (n=56): the stenosis beginning from the left main, Type II (n=58): the stenosis beginning within 3 mm of the origin of the LAD, Type III (n=44): the stenosis beginning more than 3 mm from the origin of the LAD and Type IV (n=36): the stenosis beyond the first septal perorator or the first diagonal artery. The primary success rates of the PCI and the major adverse cardiac events (MACE), during a 12-month clinical follow-up, were compared between the 4 types. RESULTS: The primary success rate was lower in the Type I than in Types II, III and IV (87.5% vs. 98.3, 97.7 and 97.2%, p=0.02). MACE, after a successful PCI, occurred in 19 [40.4%; 3 death, 2 myocardial infarction (MI) and 14 RV] of the Type I, 22 (40.0%; 1 MI, 21 RV) of the Type II, 12 (28.6%; 12 RV) of the Type III and 7 (21.2%; 1 MI, 6 RV) of the Type IV patients during the 12-month clinical follow-up (Type I and II vs. III and IV, p=0.03). CONCLUSION: LAD ostial lesions are associated with a relatively high PCI primary success rate, but with a related high MACE equivalent to left main involvement on long-term clinical follow-up.