Haemostasis is a complexly controlled process which takes place in two stages.The first initial stage leads to the formation of a small amount of thrombin. The crucial step of initiation is the bond between the activated factor VIIa and the tissue factor. It is regulated by interaction be- tween factors promoting and inhibiting the process of thrombigenesis. The initiation of haemosta- sis must be associated with the formation of the thrombus and for effective fibrinogenesis the second stage, amplification of haemostasis, is necessary. A new two-stage model of coagulation imitates the process of haemostasis in vivo as the classical MacFarlan cascade model and makes it possible to explain the pathogenesis of prothrombotic conditions.

        Key words: Coagulation - Initiation and amplification stage.