Summary: Correlation behaviours of cephalic and post-cephalic indices in the analyses of inter-group relationships have not been sufficiently explored so far. The scarcity of data for both body segments has limited this type of research. At the same time, other estimates of the ‘shape’ through ‘size’ adjustments have been proposed, with their superiority in the use of the indices being taken for granted. This assay analyses the correspondence between forms and the discriminatory efficiency of the indices, taking advantage of the data from the Vellard collection comprising 1734 aborgenes from 12 ethnic groups in the Great South Chaco. This was done using the Homogeneity Analysis (HOMALS), which calculated the own vectors and the ‘weights’ of both the variables (indices) and the groups in the main dimensions of the variation, graphically representing their location in the co-orderly system of the variables. The results show similar relationships between head-forms in men and women, but in women there is a net independence between the categories of the neural and facial portions. The greater morphological differentiation of chirts is recorded in these cephallic regions, while at the level of the post-cephalic segment the ethnicity is more similar. Inter-ethnic morphological relationships differ according to sex. Within each sex, the topology obtained is identical whether only the head or the head is taken into account together with the body. Abstract At present, the relationship between both head and body shares derived from indications has not been increased as a result of the low number of collections with cephalic and post-cephalic data, and the relocation of such ‘indications’ by other estimates of ‘shape’, anticipated ‘size’ adjustments, which have been higher than those ratios. The relationship between head and body outlets is investigated in this case through the measurements taken by J. Vellard on 1734 aborigines (890 men and 844 women) of South American “Gran Chaco”. Each individual was classified in the categories for each ratio. Homogeneity analysis (HOMALS) was applied to discover associations among Morphological Categories, as well as to place in coordinating axes both combined ethnic groups and categories in the aborigines of Chaco. The results shared similarly in head shares for both men and women, but the latter managed net independence between cephalic and facial categories. The higher Morphological variability of ‘chaquenses’ appears in such regions, while body does not seem to vary among the ethnic groups. Morphological inter-group relationships are different in men and women. However, if we see only head, or alternately both head and body, an identical topology within sex is obtained.