A total of almost 200 members of a tribal group, the Chenchu from the Mahabubnagar and Kurnool districts of Andhra Pradesh, have been tested for electrophoretic variation in a number of red cell enzyme systems. The former population has also been tested for ABO, MN and Rh blood group systems and for the serum proteins Hp, Tf and albumin. The most significant findings were the presence of the gene ry, and the occurrence of a polymorphism in PHI with the variant gene PHI5 having a gene frequency of 4%.