Background: The differential outcome of percutaneous coronary intervention (PCI) versus coronary artery bypass grafting (CABG) is not well known in patients with isolated (without remained coronary artery disease) unprotected left main coronary artery (ULMCA) disease. Methods: Between Jan, 2000 and June, 2006, a total of 364 patients with isolated ULMCA stenosis were collected from 12 academic centers in Korea. Percutaneous coronary intervention (PCI) and coronary artery bypass grafting (CABG) were performed in 291 patients and 73 patients, respectively. Results: There was no significant difference of baseline clinical and lesion characteristics among patients with PCI and CABG. The mean follow-up period was 969.1639.9 days in patients with underwent PCI and 916.2620.3 days in patients with underwent CABG. There was no difference of death or Q-wave myocardial infarction. However, patients with PCI showed a significantly higher incidence of target vessel revascularization than those with CABG (Table). Conclusions: There was no difference in death or Q-MI in patients with isolated ULMCA disease with regard to PCI and CABG. However, PCI modality was significantly associated with target vessel revascularization.