A sample of 417 individuals belonging to three Tupi‐Mondé‐speaking tribes (Gavião, Surui, Zoró) were variously studied in relation to 26 genetic protein systems. Previous investigations performed among the Surui in relation to some of these systems were confirmed. The three groups do not depart markedly from the genetic pattern already established for South American Indians and show low inter‐ethnic admixture. When these results are combined with those from 10 other Tupi tribes, two clear geographic groupings (southeastern and northwestern) can be discerned. Using different methods to evaluate the same genetic distance matrices, different patterns of association between the Tupi‐Mondé populations were obtained. The populations are probably too similar among themselves, blurring finer relationships.