Within the context of a prospective study we investigated the influence of malignant and benign breast disease on the coagulation systems both prior to and after surgery. In addition we also investigated to what extent individual risk factors aid the formation of a thrombophiliac risk profile. Altogether 50 patients with carcinomas of the breast and 12 patients with benign breast disease were included in the study. The coagulation investigations took place prior to surgery and on the 1st, 3rd, 7th and 10th day following the operation. The results have already revealed that prior to surgery a clear activation of the haemostasis takes place among patients with a carcinoma of the breast. When compared to patients with benign breast conditions there was a far greater plasma level of factor VIII vWF, fibrinogen, thrombin-antithrombin III complex, D-dimer fibrin degradation products, tissue-type plasminogen activator and the activity and the antigen of plasminogen activator inhibitor 1. Also during the postoperative period the malignant tumour was a stimulus for additional increased activity of blood coagulation and fibrinolysis. Individual risk factors such as age, menopausal status, obesity and smoking lead to a thrombogenic risk profile which could provide a possible explanation for the observed increased incidence of thrombosis in breast cancer patients. For the clinical work there is a need for intensive pre- and postoperative monitoring in the cases of patients with malignant tumours including angiological examinations, intensive physiotherapy and a risk-adapted prophylactic anticoagulation.