A survey of the blood of twenty-two patients who had undergone hepatic resection was performed. Serum levels of alpha-2 plasmin inhibitor-plasmin complex initially decreased from 1.58 +/- 0.31 microgram/ml on the preoperative day (PREOP), to 0.92 +/- 0.14 mu/ml on the first postoperative day (POD 1), and then increased to 3.13 +/- 0.92 micrograms/ml on the seventh postoperative day (POD 7) (mean +/- SE)). Thrombin-anti-thrombin III complex (14.2 +/- 4.3 ng/ml on PREOP and 26.0 +/- 4.1 ng/ml on POD 7 (mean +/- SE)) and D-dimer (335 +/- 96 ng/ml on PREOP and 1859 +/- 258 ng/ml on POD 7 (mean +/- SE)) increased in the early postoperative stage. The level of 6-keto-prostaglandin F1 alpha increased after the operations (from 13.2 +/- 1.8 pg/ml on PREOP to 37.8 +/- 12.8 pg/ml on POD 7 (mean +/- SE)). The level of thromboxane B-2 decreased at first, and then gradually increased and returned to its preoperative level on POD 7 (144.7 +/- 43.8 pg/ml on PREOP, 57.6 +/- 27.5 pg/ml on POD 1 and 152.5 +/- 58.4 pg/ml on POD 7 (mean +/- SE)). Superoxide dismutase activity increased at first, and then gradually decreased, postoperatively (2.8 +/- 0.5 NU/ml on PREOP, 4.8 +/- 0.8 NU/ml on POD 1 and 2.6 +/- 0.3 NU/ml on POD 7 (mean +/- SE)). That is, biodefensive reactions which protect patients against the shift to disseminated intravascular coagulation (DIC) were inferred with by the increase in antiplatelet aggregation, despite the activation of coagulation and fibrinolytic mechanisms after hepatic resection.