BACKGROUND Thromboembolism remains a major problem in patients scheduled for craniotomy. The present study examined parameters of coagulation and fibrinolysis in 15 patients undergoing elective craniotomy in the perioperative period. METHODS Plasma concentrations of thrombin antithrombin III complex (TAT), prothrombin fragment 1 + 2 (F1 + 2), and d-dimer were measured before and after induction of anesthesia, 60 minutes and 180 minutes after the beginning of surgery, and on the first postoperative morning. RESULTS TAT, a marker of activation of coagulation, increased significantly (p < 0.05) from the preoperative measurements to the data obtained 60 minutes after beginning the surgery, reaching a maximum of 180 minutes after the start of surgery. F1 + 2, also indicating activation, showed a similar concentration time course with an intraoperative maximum, D-dimer, a marker of fibrinolysis, tended to increase slightly beginning 180 minutes after surgery with a maximum on the morning after surgery. Statistical significance for F1 + 2 and d-dimer was not found. CONCLUSIONS This study showed a transient activation of coagulation with an intraoperative maximum in patients undergoing craniotomy. This result could be due to a liberation of thromboplastin from brain tissue. (C) 1997 by Elsevier Science Inc.