Red blood cell membrane structure and antigens. The ABO system, the Rh system and the other main blood groups. The genetics of blood groups. ABO and Rh typing. Transfusion relevance of blood groups. Red blood cell alloimmunization. Detection of anti-erythrocyte antibodies. Compatibility tests. Acute and delayed hemolytic reactions. Autoimmune hemolytic disease. Blood components: preparation, storage, quality check. Main transfusion reactions. Transfusion during pregnancy. Newborn hemolytic disease. Platelet antigens and their significance in transfusion medicine. Idiopatic thrombocytopenia. Alloimmune newborn thrombocytopenia. Post-transfusion purpura.