Aims: Contrast-media induced nephropathy (CIN) remains a common complication after contrast dye exposure especially in patients with chronic renal impairment (CRI). We sought to evaluate the efficacy of the antioxidant ascorbic acid as an adjunct to hydration in limiting the incidence of contrast induced nepbrotoxicity after coronary procedures. Materials and methods: In a randomized, double-blind, prospective, single center-study, 143 consecutive patients with CRI (creatinine level > 120 μmol/l) referred to coronary angiography/intervention were randomly assigned to receive 1 g ascorbic acid or placebo in adjunct to saline hydration prior to and after angiography. Creatinine and urea nitrogen levels were measured prior to and up to 6 days after exposure to contrast agent. Results: The development of CIN occurred totally in 8/143 (5.6%) patients. Between the two groups no significant difference was detected (Vitamin C 5/74 (6.8%) patients; placebo 3/69 (4.3%) patients). After adjusting for the amount of contrast dye, drug treatment, cardiovascular risk factors, ejection fraction, or sex, again no differences were detected. No patient required dialysis. More patients with diabetes had development of CIN (7/85; 8.2%) compared with nondiabetic patients (1/58; 1.7%), although not significant (p = 0.14). The incidence of CIN was elevated in patients with high amounts (> 140 ml) of contrast volume used (6/8). Conclusions: Our study does not support the prophylactic use of ascorbic acid in patients with renal dysfunction exposed to contrast dye.