Background Angioplasty in the unprotected left main coronary artery (LMCA) has been controversial. This study aims to evaluate the safety and clinical effectiveness of stenting, including bare metal stent and drug eluting stent (DES), for treatment of unprotected LMCA disease.Methods Between September 1997 and December 2005, a total of 297 consecutive patients underwent percutanous coronary intervention (PCI) on LMCA lesions in our hospital. Their in-hospital data and clinical follow-up outcomes were analyzed and those in pre-DES "era" (group I, from September 1997 to December 2002) were compared with those in DES "era" (groupⅡ, from January 2003 to December 2004. Patients in 2005 for the time of follow-up less than one year were not included in this group).Results Altogether 368 coronary stents were successfully deployed in 295 patients. Stents failed to be implanted after balloon predilation in two patients, who received coronary artery bypass graft (CABG) successfully. Bifurcation techniques for distal LMCA executed in 206 patients (69.4%, 206/297), included crossover stenting in 156 (75.7%), T stenting in 4 (1.9%), provisional T stenting in 28 (13.6%), kissing stenting in 5 (2.4%) and stent crushing in 13 (6.3%) patients. During their hospital stay, 5 (1.7%) patients died after PCI procedure, of which 4 died from cardiac origin and one of renal failure. The total in-hospital major adverse cardiac events (MACE) were 2.0% (6/297). In the follow-up period, 19 patients (6.5%) died [15 (5.1%) of cardiac death and 4 of non-fatal myocardial infarction (MI)]. Besides, 2 (0.7%) developed subacute thrombosis (SAT) and 16 (5.4%) performed target lesion revascularization (TLR). The total follow-up MACE was 14.5% (43/297). Further analysis also showed that, compared with patients in group I, those in groupⅡapparently had more multi-vessel involvement (14.7% vs 81.9%, P