Background: Contrast-induced nephropathy (CIN) is a complication of coronary diagnostic and interventional procedure. CIN has been associated with increased mortality and morbidity. The purpose of this study is to investigate the other possible risk factor for CIN. Methods: 537 patients who were received percutaneous coronary intervention (PCI) from Jan 2005 to Dec 2006 comprised the study group. Major exclusion criteria included serum creatinine > 4.0 mg/dl or dependence of dialysis, neoplasm, vascular malformation, thrombocytopenia, overt bleeding and blood product transfused patients. CIN was defined as an increase in serum creatinine of 25% or 0.5mg/dl above the baseline value up to 48 hours after the contrast administration. The study population were divided into 2 groups: group I [486 patients, 62.0짹11.5 years, 310 male: patients who did not developed CIN] and group II [51 patients, 64.6짹10.3 years, 29 male: patients who developed CIN]. Results: Baseline clinical and cardiovascular risk factors were not significantly different between 2 groups except body weight (Group I:Group II= 63.5짹10.6 kg:59.7짹9.2 kg, p=0.008), prePCI creatinine (Group I:Group II= 1.0짹0.4 mg/dl:1.4짹1.4 mg/dl, p=0.000), prePCI hemoglobin (Group I:Group II= 13.2짹2.0 g/dl:12.3짹2.0 g/dl, p=0.004), and postPCI hemoglobin (Group I:Group II= 12.4짹1.9 g/dl:11.5짹1.8 g/dl, p=0.001). The proportion of urgent PCI including early invasive and primary PCI (Group I:Group II=171(35.2%):23(45.1%), p=0.009) was higher in group II. Multiple logistic regression analysis showed periprocedural drop of hemoglobin (���1 g/dl) was independent predictor of CIN. Other independent predictors of CIN included: age, body weight, prePCI creatinine, and urgent PCI (Table). Conclusions: Periprocedural drop of hemoglobin more than 1 g/dl was another important independent predictor for CIN like other traditional risk factors.