Contrast media volume to creatinine clearance (V/CrCl) ratios were obtained from consecutive consenting patients after coronary angiography. Receiver-operator characteristic (ROC) curves were used to identify the optimal sensitivity for the observed range of V/CrCl. The predictive value of V/CrCl for the risk of contrast-induced nephropathy was assessed using multivariate logistic regression.Subgroup analysis was performed on patients with creatinine clearance \< 60 ml/min,diabetes,emergent angiography.