The fibrinolytic effects of six different anaesthetic agents were studied in 36 patients undergoing abdominal hysterectomy. Fibrinolytic activity was measured by dilute whole blood and euglobulin clot lysis times. Concentrations of plasminogen, fibrinogen and fibrin degradation products were also determined. Significant enhancement of fibrinolytic activity, measured as a decrease in clot lysis time, was seen during anaesthesia and surgery with all agents studied. Halothane produced the least effect and the greatest increase in fibrinolytic activity was seen during trichloroethylene anaesthesia. Lumbar extradural anaesthesia also consistently produced enhancement of fibrinolysis. The reasons for these results and their clinical implications are discussed.