Postoperative acute renal failure (ARF) is not uncommon after cardiac surgery and after angiography. However, limited information exists regarding the influence of the interval between cardiac catheterization and subsequent cardiac surgery and amount of contrast agent used during this procedure on the occurrence of postoperative ARF. Data for 423 consecutive adult patients who underwent elective cardiac surgery after cardiac catheterization were examined retrospectively. The influence of interval between cardiac catheterization and cardiac surgery on postoperative ARF (defined as postoperative serum creatinine ≥2 times baseline and >2 mg/dl and/or need for renal replacement therapy) was evaluated using multivariable logistic regression. ARF occurred in 24 patients (5.7%). Median time to angiography was 2 days (interquartile range 1 to 4.5), and median dose of contrast used was 1.36 ml/kg (interquartile range 1.12 to 1.69). Surgery on the day of cardiac catheterization was independently associated with increased risk of ARF (adjusted odds ratio 3.1, 95% confidence interval 1.1 to 8.8). This risk of ARF was highest in patients who underwent surgery on the same day as angiography and with a dose of contrast higher than median (14.6%) and lowest when surgery was delayed beyond 1 day of angiography and contrast dose was median or less (2.4%; adjusted odds ratio for same-day surgery and dose higher than median 4.2, 95% confidence interval 1.2 to 14.2). Cardiac surgery performed on the day of cardiac catheterization and higher dose of contrast agent used were both independently associated with increased risk of postoperative ARF. In conclusion, these findings suggest that delaying cardiac surgery beyond 24 hours of exposure to contrast agents (when feasible) and minimizing the use of these agents have significant potential to decrease the incidence of postoperative ARF in patients undergoing elective cardiac surgery.