With his discovery of the ABO blood group system, Karl Landsteiner laid the foundation for modern day transfusion medicine. This discovery represents the basic knowledge for every blood transfusion. In recent years, certain blood groups have been linked to an increased risk for certain diseases. Hence, teaching the blood group serology is a relevant issue in medical education. In this review, we report about the history of the discovery of the blood groups by Landsteiner, the link of different blood groups to certain diseases and our experiences regarding teaching to medical students.