Abstract.Nineteen African tribes living in Uganda have been studied for ABO and Rh(D)antigens. High incidences of group A (41%), group B (30%), and group O (51%) were found in the tribes of West Nile, Busoga‐Bukedi, and Karamoja, respectively. Genetical mixing showing a southwestward ‘cline’ is apparent. The northern, eastern and central regions have less Rh(D)‐negative than the western region. The incidence of Rh(D)‐negatives increases from the north (less than 2%) to the south (about 6%).In the Kampala area, incidence is A 27%, B 20%, O 48%, AB 5%, and Rh(D)‐negative 2%. It is recommended that transfusion of blood without Rh(D)typing be discouraged. The practice would be more dangerous in the western regio