BACKGROUND: The optimal revascularization strategy for patients with left main coronary artery disease (LMCAD) and chronic kidney disease (CKD) remains unclear. OBJECTIVES: This study investigated the comparative effectiveness of percutaneous coronary intervention (PCI) versus coronary artery bypass graft (CABG) surgery in patients with LMCAD and low or intermediate anatomical complexity according to baseline renal function from the multicenter randomized EXCEL (Evaluation of XIENCE Versus Coronary Artery Bypass Surgery for Effectiveness of Left Main Revascularization) trial. METHODS: CKD was defined as an estimated glomerular filtration rate <60 ml/min/1.73 m2 using the CKD Epidemiology Collaboration equation. Acute renal failure (ARF) was defined as a serum creatinine increase ≥5.0 mg/dl from baseline or a new requirement for dialysis. The primary composite endpoint was the composite of death, myocardial infarction (MI), or stroke at 3-year follow-up. RESULTS: CKD was present in 361 of 1,869 randomized patients (19.3%) in whom baseline estimated glomerular filtration rate was available. Patients with CKD had higher 3-year rates of the primary endpoint compared with those without CKD (20.8% vs. 13.5%; hazard ratio [HR]: 1.60; 95% confidence interval [CI]: 1.22 to 2.09; p = 0.0005). ARF within 30 days occurred more commonly in patients with compared with those without CKD (5.0% vs. 0.8%; p < 0.0001), and was strongly associated with the 3-year risk of death, stroke, or MI (50.7% vs. 14.4%; HR: 4.59; 95% CI: 2.73 to 7.73; p < 0.0001). ARF occurred less commonly after revascularization with PCI compared with CABG both in patients with CKD (2.3% vs. 7.7%; HR: 0.28; 95% CI: 0.09 to 0.87) and in those without CKD (0.3% vs. 1.3%; HR: 0.20; 95% CI: 0.04 to 0.90; pinteraction = 0.71). There were no significant differences in the rates of the primary composite endpoint after PCI and CABG in patients with CKD (23.4% vs. 18.1%; HR: 1.25; 95% CI: 0.79 to 1.98) and without CKD (13.4% vs. 13.5%; HR: 0.97; 95% CI: 0.73 to 1.27; pinteraction = 0.38). CONCLUSIONS: Patients with CKD undergoing revascularization for LMCAD in the EXCEL trial had increased rates of ARF and reduced event-free survival. ARF occurred less frequently after PCI compared with CABG. There were no significant differences between PCI and CABG in terms of death, stroke, or MI at 3 years in patients with and without CKD. (EXCEL Clinical Trial [EXCEL]; NCT01205776).