The red blood cells of the group A infant of a group O central African Negro woman of the Zezuru tribe with anti-Lea and anti-JSb in her serum were found to be strongly agglutinated by a commerical antiglobulin reagent six days after birth. The high concentration of bilirubin in the infant's serum gradually decreased but he became profoundly anemic and, in the absence of a suitable donor, was successfully transfused with blood from his mother. Subsequent tests using the maternal anti-JSb diluted one in ten to avoid agglutination by the anti-Lea showed that the frequency of the JS(b-) phenotype in group O Zezuru is approximately one per cent.