Data have emerged demonstrating the safety and efficacy of percutaneous coronary intervention (PCI) of the unprotected left main (ULM) artery. The 2009 American College of Cardiology/American Heart Association/Society for Cardiovascular Angiography and Interventions focused guidelines for PCI no longer state that ULM PCI is contraindicated in patients with anatomic conditions that are associated with a low risk of procedural complications and clinical conditions that predict an increased risk of adverse surgical outcomes. ULM PCI should be performed by operators with experience in the management of the anatomic complexities of left main and multivessel disease, specifically in issues relating to bifurcation disease, calcification, and hemodynamic support. Patients with ostial or shaft disease have lower risk of restenosis compared with distal bifurcation disease. Drug-eluting stents (DES) should be used whenever possible as they reduce clinical restenosis. Intravascular ultrasound is an integral component of the procedure as it provides accurate assessment of lesion severity and can confirm optimal stent expansion and apposition. Compliance with dual antiplatelet therapy for at least 12 months is essential if DES are used. A collaborative, multidisciplinary approach with a “Heart Team” represented by a cardiac surgeon, interventional cardiologist, and non-invasive cardiologist may optimize patient education and objective decision making when obtaining informed consent. Application of clinical and angiographic variables into risk models facilitates appropriate patient selection. Randomized clinical trials will address unanswered issues and help build consensus between cardiology and surgical societies to inform clinical decision making and optimize the outcomes for patients with ULM coronary artery disease. © 2011 Wiley Periodicals, Inc.