Relevance of platelet transfusion is related to an increasing number of indications due to conditions with an increased risk for hemorrhage and a lack of standard protocols both for treatment and prophylaxis of thrombocytopenia, in the presence of high costs of this procedure. The appropriate use of platelet transfusion is associated with reduction of thrombocytopenia, which actually in a critically ill patient is associated with increased length of stay both in intensive care unit and hospital. In 2003, the Professional Consensus was established to define the main recommendations for platelet transfusion. Not only the number of platelets but also the presence of critical conditions (disorders of thermoregulation, trauma, head brain damage, etc.) increasing the risk for bleeding is relevant. It is recommended that the platelet count in one dose of platelets transfused would be not lower than 55 x 10(9)/L in order to increase the platelet count by 5-10 x 10(9)/L. The effectiveness of platelet transfusion is evaluated 10-60 min, 18 hours, and 24 hours after transfusion. Advantages of platelet transfusion of small and large doses are presented.