Thromboelastography is a study of the elasticity of a blood clot with a thromboelastograph device. The test blood is poured into the cuvette of the device. In the blood drop the rod, hanging on a steel string. A special device is attached to the cuvette. Movement of the cuvette is not transmitted to the stem until the blood is liquid. When the blood coagulates, fibrin adheres to the stem, and it begins to swing. The mirror attached to the rod reflects a beam of light on the photo paper. A wavering beam of light draws on the photo paper a curve - a thromboelastogram. Some of its parts characterize certain phases of blood clotting: thromboplastin formation, clot formation, time of complete clotting. By the amplitude of the oscillations, the density and elasticity of the bunch can be determined. On them it is possible to deduce still a number of the sizes characterizing coagulation of blood . Thromboelastogram allows to some extent to be guided in character of infringements of coagulating system of blood.