Objective: To compare myocardial revascularization (MR) with and without extracorporeal circulation (ECC) in regard to postoperative bleeding and the need for blood and hemoderivate transfusion., Methods: From November 2001 to February 2002, 186 patients undergoing myocardial revascularization were assessed, excluding those who underwent associated procedures. The patients were divided into 2 groups as follows: group A -- comprising 116 patients undergoing MR with ECC; and group B -- comprising 69 patients undergoing MR without ECC. Both groups were comparable in regard to pre- and intraoperative characteristics, except for the greater number of distal anastomoses (P=0.0004) in group A, and greater prothrombin activity (P=0.04) and INR (P=0.03) in group B. To avoid discrepancies between the groups, 140 patients with statistically similar characteristics were selected., Results: Studying the paired groups, both the total bleeding volume in 24 hours (P=0.001) and the bleeding volume indexed for body surface (P=0.004) were greater in group A (609.6 +/- 395.8 mL; 331.8 +/- 225.8 mL/m2, respectively) than in group B (437.2 +/- 315 mL; 241 +/- 173.9 mL/m2, respectively). Although the need for transfusion was not significantly different between the groups (P=0.1), the amount of erythrocyte concentrate transfused was greater in group A (P=0.01). No statistical difference was observed in regard to transfusion of other hemocomponents and the need for surgical review of hemostasis., Conclusion: Myocardial revascularization without ECC was more advantageous than MR with ECC in regard to smaller postoperative blood loss and a lesser need for transfusion of erythrocyte concentrate. The repercussions of this finding may be innumerable, particularly in regard to minimization of morbid factors and hospital costs.