Blood samples of talapoin (19), patas (34) and vervet (6) monkeys were compared for haemoglobins, certain serum proteins and the red cell enzymes, 6PGD, G6PD, AK, PGM, LDH, acid phosphatase and achromatic bands using starch gel techniques. On the whole the electrophoretic patterns of all these proteins were very similar in the three genera and resemble the patterns found in other Old World monkeys. Individual variations of 6PGD were frequent in patas and this was the only definite polymorphism detected.