Left main coronary artery disease, present in 5-9% of patients with angina pectoris, is associated with high mortality risk when treated medically. For several decades coronary artery bypass grafting (CABG) has been regarded as the treatment choice for unprotected left main coronary artery (ULMCA) disease patients. However, proximal location and large caliber of the left main has set challenge for interventional cardiologists. Recent clinical guidelines have stated that elective percutaneous coronary intervention (PCI) can be considered for patients with ULMCA disease, although suggesting that the aggregated evidence favors CABG. A number of registry reports, as well as a substudy from a large, randomized trial, have indicated that PCI may be an acceptable alternative to CABG in some patients with ULMCA stenosis. PCI already offers tangible short-term advantages over CABG as it is less invasive, reduces hospitalization duration, avoids the disability of surgical recovery, and allows patients to subsequently have CABG if necessary.