The haptoglobin type observed in both species is electrophoretically equivalent to Hp 1–1 in man and the complete immunological identity of this protein in higher apes and man has been demonstrated by other authors. Serum haptoglobin concentration in chimpanzees is very similar to the values found in man, showing also the same age variation. On the other hand, there is no sexual difference. The values for gorillas are lower, but may be merely approximate, due to the modest number of individual