Background Contrast-induced nephropathy (CIN) frequently complicates cardiac catheterization, so the objectives of present study were to investigate the usefulness of cystatin C before catheterization and establish a cut-off level for CIN, and to examine the changes in cystatin C and several other markers in patients with and without CIN. Methods and Results Prospective study of consecutive 87 patients who underwent elective catheterization: moderate renal disease defined as glomerular filtration rate 30-59 ml · min^-1 ·1.73 mm^-2; cystatin C and creatinine (Cr), urinary liver-type fatty acid-binding protein (L-FABP), α₁, β₂ microglobulins, N-acetyl-β-D-glucosaminidase, and microalbumin were measured immediately before, and 1, 2, and 3 days after catheterization. CIN occurred in 18 patients and receiver-operating characteristic analysis showed a higher area-under-the-curve for cystatin C compared with serum Cr (0.933 vs 0.832 p=0.012). At a cut-off level of >1.2 mg/L, cystatin C before catheterization exhibited 94.7% (95% confidence interval: 0.851-1.015) sensitivity and 84.8% specificity for detecting CIN. Cystatin C levels were higher in CIN patients than in those without CIN, even before catheterization (cystatin C: 1.08±0.22 vs 1.36±0.28 mg/L, p=0.007). Urinary L-FABP was increased on days 1 and 2 in patients with moderate renal disease. Conclusion Cystatin C was useful for predicting the occurrence of CIN. Urinary L-FABP was the only marker of transient renotubular damage. (Circ J 2008; 72: 1499 - 1505)