Background: Contrast medium induced nephropathy has been associated with increased in-hospital morbidity and mortality in connection with percutaneous coronary intervention(PCI). Purpose: The aim of this study is to evaluate clinical and laboratory risk factors of contrast medium induced nephropathy (CIN). The risk of CIN might vary with individual estimated glomerular filtration ratio (eGFR) and co-existence of other risk factors. Method: In this single center prospective study, 110 patients who underwent elective percutaneous coronary were enrolled from April 2008 to July 2008. The eGFR of patients was calculated by MDRD (Modification of Diet in Renal Disease Study) equation before and 24hr/48hr after PCI subsequently. CIN was defined as a 25% elevation or an absolute increase of 0.5mg/dL in the serum creatinine level. We estimated systemic exposed contrast agent amount by contrast medium dose (grams iodine; g-I) to eGFR(ml/min) ratio(g-I/eGFR). Result: Overall, CIN occurred in 8 patients (7.3%). All patients were grouped by quartiles based on g-I/eGFR level and all cases of CIN were occurred in 3rd and 4th quartiles(low eGFR group). On univariate analysis, contrast medium dose/body surface area (P=0.03), eGFR(P=0.09) and g-I/eGFR (P=0.02) were significantly higher in CIN group. The type of contrast medium (iohexol versus iodixanol) did not affect to the risk of CIN in this study. On multivariate analysis and receiver operation characteristic curve, g-I/eGFR level was most valuable independent predictor among all of risk factor for CIN (P=0.003, Odd ratio (OR)=13.07, CI 2.4-70.3). Conclusion: Systemic exposure of contrast medium compared to eGFR level is a most valuable predictor of CIN. Contrast medium dose to eGFR(g-I/eGFR) appear to be a useful pharmacotoxic model to assess CIN risk. Limiting the contrast medium dose compared to pre-procedural eGFR level may reduce the risk of CIN.