Extradural anaesthesia is associated with lower incidences of deep vein thrombosis after total knee arthroplasty. It is not known if the type of anaesthesia influences thrombogenesis or fibrinolysis during knee surgery performed under tourniquet. We studied 31 patients allocated randomly to receive either extradural or general anaesthesia for primary unilateral total knee arthroplasty performed under tourniquet. Radial artery blood samples were obtained before surgery, during surgery with the tourniquet inflated and on deflation of the tourniquet. Plasma samples were assayed for markers of thrombin generation and fibrinolysis. Two of the circulating indices of thrombin generation, fibrinopeptide A and thrombin-antithrombin complexes, increased to a similar degree in the perioperative period in both groups. Fibrinolytic activity was similar in both groups, as measured by tissue plasminogen activator (t-PA) antigen, t-PA activity, t-PA-plasminogen activator inhibitor complexes, alpha 2-plasmin inhibitor-plasmin complexes and D-dimer. Extradural and general anaesthesia did not result in significant differences in either thrombin generation or fibrinolytic activity during total knee arthroplasty performed under tourniquet.