Blood transfusion, which has been conducted as a basic medical procedure since 17th century, is a supportive therapy to compensate loss of each blood component. All blood materials are donated, and alive and subject to decay, type-dependent for transfusion, vary in quality, may induce severe adverse reactions, such as anaphylaxis, and may transmit infectious agents. Therefore, not only the scientific and clinical decisions but also ethical considerations should be focused on for their use. All blood products are determined as "Products Derived from Specific Organism" by the Pharmaceutical and Medical Devices Law in Japan. Of note, blood management systems are different among countries; the Japanese Red Cross Society is a unique organization that collects and manufactures blood products under supervision of the Japanese Government. It establishes a hemovigilant system by which it collects all the information concerning transfusion-related adverse events and provides them to the responsible transfusion service staff of each hospital. Physicians should check all the information from the Japanese Red Cross and refer both the "Guidelines for Blood Transfusion" and "Guidelines for the Usage of Blood Products" by the Ministry of Health, Labor and Welfare for transfusion practice.