We studied the reliability of Hickman catheter (HC) blood for the determination of activation markers of coagulation and fibrinolysis in 14 patients with hematological malignancies. 10 of 22 HC samples were contaminated with heparin, probably as a consequence of our institutional antithrombotic catheter care, and withdrawn from statistical analysis. Prothrombin activation fragment F1.2, thrombin-antithrombin III complexes, soluble fibrin, degradation products of fibrinogen and fibrin, total degradation products, alpha 2-antiplasmin and antithrombin III levels withdrawn from Hickman catheters did not differ significantly from peripheral venous blood samples. Fibrinogen levels were slightly but significantly higher in peripheral venous blood samples. We conclude that Hickman catheter blood gives reliable results for the determination of activation markers of coagulation and fibrinolysis in patients with hematological malignancies, but may be less useful in clinical practice due to frequent heparin contamination.