We studied 316 patients undergoing cardiopulmonary bypass for coronary artery surgery in order to determine perioperative risk factors for postoperative renal dysfunction. A preliminary univariate analysis was performed by chi 2 analysis for categorical data and Mann-Whitney U-test for continuous variables to detect significant correlations between each risk factor and the occurrence of moderate or severe renal dysfunction. Subsequently, a multiple logistic regression was applied to the three risk factors identified as predictive for severe renal dysfunction. Low cardiac output syndrome and need for banked blood transfusions combined with a low haematocrit value during cardiopulmonary bypass increase the probability of severe renal dysfunction in the postoperative course.