In 30 patients the number of thrombocytes was determined 24-48 hours after surgical interventions and compared with the normal range. The function of thrombocytes was determined by the method of pressure registration in combined thrombocyte-aggregation-adhesion (DKTA method). In spite of the occurring thrombocytosis there is a tendency towards a decrease of response in most cases and thus of haemostatic function of blood platelets. The influence of the thrombocyte function caused by fibrinolytic split products or by a change of prostaglandine metabolism is discussed.