Previously, blood was considered irreplaceable in the body because its use in therapy had harmful, even fatal consequences for the patients transfused, to the extent that the success of a transfusion was due to chance. Our hypothesis: here in Kinshasa, many people are still unaware of their blood groups, which makes it difficult to carry out blood transfusions. If necessary (accidents, accidental childbirth, comas, etc.), we believe that knowledge of blood groups among the people of Kinshasa could reduce transfusion accidents. Our objective will be to highlight the importance of knowing one's blood group in life prevention and to find out about the distribution of blood groups in the world population as a whole. Our work focuses on transfusion safety and the fight against haemolytic disease. For our research, it consists in the knowledge of the blood group of the ABO system and that thanks to the work of LANDSTEINER that we knew that there were in the blood of the human ones the antigens (Ag) and the antibodies (Ac) defining the various blood groups.