BACKGROUND Contrast-induced nephropathy (CIN) has been recognized as a serious complication of diagnostic coronary angiography and percutaneous coronary intervention (PCI), and has been associated with prolonged hospitalization and adverse clinical outcomes. A key step to minimize the risk for developing CIN is to identify patients at risk for CIN. RESULTS We retrospectively investigated clinical factors associated with the development of CIN in 60 stable angina patients who had undergone elective PCI. The frequency of CIN was 13% (8/60). There were neither any significant differences in age, gender, baseline serum creatinine or hemoglobin levels, nor in the rate of diabetes mellitus between the CIN and the non-CIN group. However, the estimated glomerular filtration rate (eGFR) was significantly lower (40.4+/-11.4 mL/min/1.73 m(2) vs. 57.4+/-22.6 mL/min/1.73 m(2), p=0.044), and number of treated vessels (1.5+/-0.8 vs. 1.2+/-0.4, p=0.039) and stents used (2.1+/-0.6 vs. 1.4+/-0.6, p=0.007) were significantly higher in the CIN group. In addition, the amount of contrast medium was significantly larger (272+/-37 mL vs. 201+/-62 mL, p=0.003) and the contrast medium volume (CMV) to eGFR ratio (CMV/eGFR) was significantly greater (7.4+/-2.9 vs. 4.0+/-2.0, p=0.0001) in the CIN group. Stepwise regression analysis showed that the CMV/eGFR ratio was a significant independent predictor of CIN (p=0.035). At a cut-off point of >5.1, the CMV/eGFR ratio exhibited 87.5% sensitivity and 74.5% specificity for detecting CIN. CONCLUSIONS The CMV/eGFR ratio could be a useful predictor of CIN developing after elective PCI.