SUMMARYSerological HLA types (A, B, C, DRandDQloci) were studied in five different Indian tribes (Cubeo, Tucano, Coreguaje, Embera and Noanama) belonging to two distinct linguistic families. For all the MHC loci, the range of variation among the five tribes was enormous. Two tribes, Cubeo and Tucano, showed a wide spectrum of antigenic specificities which seemed to be due to admixture from non‐tribal groups, while in the other three tribes the polymorphisms of variousHLAloci showed restricted distributions. The gene frequency data, when converted to a kinship matrix and a two‐dimensional eigenvector plot, indicated that members of the same linguistic family tend to have greater genetic affin