Coagulation studies and the J-125-fibrinogen-uptake-test for diagnosis of deep vein thrombosis were carried out in 244 and 288 patients resp. undergoing vaginal or abdominal hysterectomy. They were given a prophylaxis with 2 X 5000 IU calcium heparin (Calciparin) or 2 X 5000 IU sodium heparin with 0.5 mg dihydroergotamine (Heparin-Dihydergot). Control patients received acenocoumarol (Sintrom). The incidence of deep vein thrombosis was lowest in the heparin/dihydroergotamine group and was 5.9%. With calcium heparin prophylaxis it was 15.5%, and with acenocoumarol 12.2%. Plasma heparin levels and parameters of coagulation, fibrinolysis and platelet function showed that after 8 days of heparin prophylaxis with or without dihydroergotamine there is no change in hemostasis towards an increasing hypo- or hypercoagulability. Coagulation changes and the incidence of postoperative wound hematoma were identical using heparin alone or in combination with dihydroergotamine. Thus the improved effectiveness of heparin/dihydroergotamine in prevention of deep vein thrombosis which has been shown in the fibrinogen test cannot be explained by an effect onto the coagulation parameters studied. It is pointed out that a peridural anesthesia can be carried out in low-dose heparin and heparin/dihydroergotamine prophylaxis without the risk of bleeding and that the incidence of wound hematoma can be reduced by correct choice of the site of injection.