In the past, coronary artery bypass graft surgery has been applied to revascularization for unprotected left main coronary artery (ULMCA) disease. In recent years, due to the advent of drug-eluting stents (DES), restenosis rates have decreased in comparison to conventional bare-metal stents (BMS), and the range of applications of percutaneous coronary intervention (PCI) for ULMCA disease has been expanded. However, even if DES is used, outcomes of PCI for distal left main coronary artery bifurcation lesions are not sufficient. Moreover, problems specific to DES, such as late stent thrombosis and late catch-up phenomenon, have been identified. There are still unknown points regarding remote-stage outcomes of DES. Thus, further investigation is needed on PCI for ULMCA disease, along with further analysis of remote-stage outcomes of BMS.