Blood bankers first became aware of the Kidd blood group system in the early 1950s. Since that time, the Kidd system has garnered and retained a reputation amongst transfusion medicine professionals as being especially significant. Its antibodies, though often difficult to detect, are a common cause of hemolytic transfusion reactions. This session will cover a primer of the Kidd blood group system and give a wide range of information about the antigens and antibodies associated with it.