Unprotected left main (LM) coronary artery disease (CAD) represents a challenging lesion with a major prognostic impact.Evaluate the clinical outcome and major adverse cardiac events (MACE) predictors of unprotected LM percutaneous coronary intervention (PCI) in an "all-comers" population.We performed a prospective observational study of patients with unprotected LM stenosis treated by PCI. MACE were defined as the composite endpoint of all-cause death, myocardial infarction and target lesion revascularization.From January 2012 to December 2017, 150 consecutive patients who underwent unprotected LM PCI were included. The mean age was 64±12 years and 75.3% were males. Diabetes was noted in 50.7%. Emergent revascularization was performed in 20.7% of cases, including 3.3% patients with cardiogenic shock. Distal LM was involved in 76.7% of cases. A majority of patients (94.0%) had low or intermediate SYNTAX Score I (≤32). The median SYNTAX score II was 31.1. Drug-eluting stents were used in 78.7% and bare metal stents in 21.3% of patients, mainly in emergent setting where the former were unavailable. In distal LM PCI, provisional approach was mostly used (81.7%). The median follow-up was 13.4 months. MACE occurred in 23.3% with an estimate of 37.9% at 5 years. Significant predictors of MACE were cardiogenic shock, bare metal stents use, previous PCI, and SYNTAX score II ≥30.Unprotected LM PCI presents encouraging short and long term outcomes. SYNTAX score II might represent a predictor for long-term outcome in this particular lesion subset.