Radiocontrast-induced nephropathy (RCIN) after percutaneous coronary intervention (PCI) is associated with grave consequences, but risk stratification of patients has not been well elucidated. This analysis derived a time-insensitive score to predict the risk of RCIN after PCI. A derivation cohort (1993 to 1998) and a validation cohort (1999 to 2002) comprised 20,479 patients who underwent PCI. RCIN after PCI was defined as a >/=1.0 mg/dl increase in serum creatinine. Variables having an independent correlation for RCIN after PCI were used to derive the RCIN risk score from the derivation cohort and were tested in the validation cohort. RCIN occurred in 2% of patients after PCI. Independent variables (with weighted scores) include estimated creatinine clearance <60 ml/min (2), urgent PCI (2), intra-aortic balloon pump use (2), diabetes mellitus (1), congestive heart failure (1), hypertension (1), peripheral vascular disease (1), and contrast volume >260 ml (1). The incidence of RCIN after PCI increased with each unit increase in score (p <0.0001, concordance statistic 0.89). No patient with a score </=1 developed nephropathy, whereas 26% of patients with a score >/=9 developed RCIN after PCI (p <0.0001). Propensity score analysis showed that patients who developed RCIN after PCI, irrespective of the need for hemodialysis, had higher in-hospital rates of major adverse cardiac events (odds ratio 15, 95% confidence interval 11 to 20, p <0.0001). RCIN occurred in 2.0% of PCI patients and was associated with a 15-fold increase in adverse cardiac events. The RCIN risk score was a clinical assessment tool with excellent predictive ability in identifying the larger population at risk for nephropathy in whom preventative strategies are indicated.