In this study, we evaluated the effects of anticoagulants used in blood sampling on the measurements of coagulation activation markers F1 + 2, TAT, D-Dimers by Elisa methods. The study was carried out on normal subjects and patients with inherited deficiency of coagulation inhibitors, antithrombin III (ATIII) protein C (PC) and protein S (PS). Three different anticoagulant solutions were compared: 1) ACD/EDTA/adenosine/heparin, 2) EDTA/aprotinin/a synthetic thrombin inhibitor and 3) sodium citrate. The results showed that sodium citrate, commonly used in coagulation laboratories, is a suitable anticoagulant for the study of coagulation activation markers. In addition, the type of tubes (plastic tubes vs glass Vacutainer R tubes) used for blood sampling as well as the order of sampling (early or late after the phlebotomy procedure) did not influence the results. We concluded that assays of coagulation activation markers F1 + 2 and D-Dimers can be performed in samples collected routinely by haemostasis laboratory staff using Vacutainer R tubes with sodium citrate. Further investigations are needed to understand why TAT measurements gave a pattern of results quite different from F1 + 2 or D-Di measurements.