BACKGROUND Open heart surgery still involving major bleeding continues to be a major challenge after cardiac surgery and is also a significant cause of morbidity and mortality. Most hemostatic factors are intercorrelated with postoperative bleeding, and fibrinogen seems the most fundamental hemostatic risk factor for open heart surgery. METHODS The study included 97 patients who underwent elective coronary artery surgery (78 men and 19 women; mean age, 60.9 +/- 10.3). Preoperative blood samples were obtained and preoprative quantitative determination of plasma fibrinogen levels were measured by the clotting method of Clauss using the fibrinogen kit. Patients were operated on by the same team and the same technique. The total amount of drainage blood from chest tubes was recorded after termination of operation. RESULTS There were statistical significance between the fibrinogen levels and the drainage (r = -0.897, P < .001). Chest drainage was a mean of 972 mL (range, 240-2445 mL) in the first 48 hours after sternotomy closure. Fibrinogen level and relation to age was statistically significant (P = .015). There was no statistical significance between fibrinogen levels and gender (male gender = 400.7 +/- 123.0 versus female gender = 395.6 +/- 148.1; P = .877) and between drainage and gender (male gender = 968.2 +/- 538.5 versus female gender = 990.0 +/- 554.7; P = .876). Two patients (2%) died early after the surgery. There were no significant differences between the postoperative bleeding and cardiopulmonary bypass time (P = .648) or cross-clamp time (P = .974). CONCLUSIONS The results of this study suggested that low preoperative fibrinogen level appears to be a useful diagnostic marker to assess the activity of the coagulation system, and that its preoperative level may serve as a potential risk factor for postoperative bleeding after coronary artery bypass surgery.