Measurements of height, face height, nose height, nose breadth, head length and head breadth from individuals living in 17 villages of six South American Indian tribes were compared using Mahalanobis's morphological distances and their partition into size and shape components. Total D2 values correlate well with estimates of linguistic differentiation, but not with geographic distances between tribes. Three of the six tribes were also studied for blood polymorphisms, and again measures of distances based on these haematological traits did not correlate well with the morphological ones. The shape component was about three times as important as size in contributing to the intertribal variation.