OBJECTIVE Platelet dysfunction is one of the major reasons of postoperative bleeding following coronary artery surgery. The aim of this study was to evaluate the effects of clopidogrel; a specific and potent irreversible inhibitor of platelet aggregation; on bleeding and use of blood and blood products after coronary artery bypass surgery (CABG). METHODS Preoperative patient characteristics and perioperative and postoperative data were collected prospectively in 1628 consecutive patients undergoing isolated CABG performed by the same surgical and anesthesia team. Of these, 48 were receiving clopidogrel preoperatively. Of the 1628 patients, 1456 underwent elective and 172 (10.6%) underwent non-elective operation. Thirty-six (2.5%) of the elective patients and 12 (7%) of the non-elective patients were using clopidogrel, preoperatively. Baseline characteristics, chest tube output, and the need for reexploration or for blood and blood product transfusion of clopidogrel recipients and non-recipients were compared. The clopidogrel group had higher prothrombin time level (12.6+/-1.6; 11.5+/-1.7 s, (P=0.013), however comparable aPTT level (32.6+/-4.5 vs. 31.4+/-4.5 s), and platelet count (275,000+/-98,000 vs. 280,000+/-72,000 dl(-1)). RESULTS The need for reexploration or for blood and blood product transfusion, chest tube output, ICU length of stay (20.1+/-2.9 vs. 21.9+/-13.5 h; P=NS), and hospital length of stay (5.5+/-1.7 vs. 5.4+/-2.1 days; P=NS) were similar in clopidogrel recipients and non-recipients, respectively. Further analysis demonstrated no significant difference in use of homologous blood or fresh frozen plasma, amount of postoperative bleeding and reoperation rates for bleeding as well as length of intensive care unit and hospital stay between the clopidogrel and the control groups both in elective and non-elective patients. CONCLUSIONS The results of this study suggest that preoperative use of clopidogrel is not associated with increased bleeding and need for surgical exploration as well as risk of blood and blood product transfusion after CABG.