A slide presentation Dr. Yamamoto gave at Osaka University was modified to prepare the following web pages. The most up-to-date unpublished information has been omitted. Nonetheless, you may still learn the basics of ABO genes, A and B transferases, and ABH antigens from this material. You may also obtain a clear view of both what has been answered and what remains to be achieved scientifically in the study of the ABO system. If you would like a copy of the PowerPoint file of this presentation for use in your curriculum, etc., please contact Dr. Yamamoto at email@example.com.