Background: Data are limited about important risk factors for long-term mortality in patients undergoing percutaneous coronary intervention (PCI) for unprotected left main coronary artery (ULMCA) disease. Methods: Between Jan, 2000 and June, 2006, a total of 1141 patients with ULMCA stenosis underwent coronary stenting at 12 academic institutions in Korea. Bare-metal stents (BMS) and drug-eluting stents (DES) were implanted in 336 and 805 patients, respectively. Results: During long-term clinical follow-up (median 33.3 months, IQR 22.6-47.9), 75 patients died with 3-year cumulative incidence of 7.1%. After multivariable Cox regression analysis, use of durg-eluting stent (DES), previous congestive heart failure (CHF), chronic renal failure (CRF), high Euroscore (���6), chronic obstructive lung disease (COPD), and average stent size were major predictors for all-cause mortality in the overall PCI patients. In patients treated with BMS, high Euroscore (���6), average stent size were identified as independent predictors of mortality. In patients treated with DES, previous CHF, CRF, COPD, high Euroscore (���6), and intravascular ultrasound guidance were major predictors of mortality. (Table) Conclusions: Several clinical, lesion, or procedural characteristics were identified as important predictors for long-term mortality in patients undergoing PCI for ULMCA, showing stent-specific differences in relative weight of prognostic factors.