Objectives: To determine the impact of the level of kidney function on the extended (>5 years) long-term clinical course of patients undergoing percutaneous coronary intervention (PCI). Background: Chronic kidney disease (CKD) has been significantly associated with an increased in-hospital and 1-year mortality following PCI. Methods: In this single-centre retrospective study, glomerular filtration rate (GFR) at baseline was estimated in 371 patients not on dialysis, who underwent successful PCI between mid-1995 and mid-1999. Baseline demographic and angiographic characteristics, and long-term major adverse cardiac events and symptoms were compared for patients with GFR ≥60 ml/min/1.73 m2 (normal or mildly impaired renal function) and GFR ≥ 60 ml/ min/1.73 m2 (CKD). The independent effect of GFR, modelled both as a categorical and a continuous variable, on long-term clinical outcomes was also investigated using multivariate Cox regression analysis. Results: Nine-year all-cause and cardiac mortality rates were significantly higher in the CKD group (45.9% vs. 10.6%, P < 0.0001 and 35.4% vs. 7.1%, P < 0.0001 respectively), while there was no difference in the repeat revascularization (P = 0.27) and nonfatal Q-wave myocardial infarction (P = 0.74) rates. Multivariate analysis demonstrated an independent impact of the level of GFR on long-term mortality; adjusted 9-year all-cause and cardiac mortality increased by approximately 16% and 11%, respectively for a decrease of GFR from 120 to 60 ml/min/1.73 m2 and by approximately 14% and 9%, respectively for a decrease of GFR from 60 to 30 ml/min/1.73 m2. Conclusions: The level of renal function is a strong determinant of long-term all-cause and cardiac mortality after successful PCI. © 2006 Wiley-Liss, Inc.