Hemostasis can be characterized as an array of physiological mechanisms providing both blood fluidity in the intact blood vessels and hemostasis in the event of impaired continuity of the blood vessel wall. The impaired hemo-static balance may lead on the one hand to an increased tendency to bleed, either spontaneously or only in response to an external stimulus. At the opposite end of bleeding are thrombophilic conditions characterized by an increased tendency to blood coagulation and thereby to the development of venous or arterial thrombosis. The hemostatic balance is the result of normal functioning of the blood vessel wall, platelets and plasma agents which include the coagulation and fibrinolytic systems and their inhibitors. By coagulation we understand the process leading to the formation of fibrin networks including the controlled interaction of coagulation factors. It is a physiological process as opposed to thrombosis which can be defined as increased coagulation under pathological conditions. Key words: coagulation - coagulation factors - coagulopathy - hemophilia - inhibitors of coagulation factors deficiencies - purpura - thrombocytopathy - thrombocytopenia.