Controversies remain about the bacteriologic aspects of intraoperative blood salvage despite the widespread use of this technique. In this prospective study, intraoperative salvaged blood was cultured in 401 patients, according to a direct plating technique. Bacterial growth was detected in 12.7% of cases. These results were compared with those obtained in control studies with sterile water and blood bank units under the same culture conditions. Most microorganisms were coagulase-negative staphylococci, followed by other skin and environmental contaminants. Quantitative estimates of contaminations showed low counts of colony-forming units (CFU/ml): 82% of positive cultures yielded 1 or 2 CFU/ml and 6% had 5 to 20 CFU/ml. Patients were followed up for a minimum of 3 months to detect septic complications. No statistically significant correlation could be found between bacteriologic results of autotransfused blood and infectious complications. This study suggests that bacteriologic monitoring of patients who have undergone autotransfusion may help in detecting surgical field contamination. It also confirms that intraoperative autotransfusion adds little septic risk to cardiac surgery.