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Palm and finger prints of 203 male and 202 female individuals are reported from four linguistic groups composed of 10 Brazilian Mato Grosso Indian tribes. Significant differences within the series are not extensive but more than expected by chance. The dermatoglyphic features accord with those regarded as characteristic of South American Indians. The frequencies of digital whorls, thenar patterns, axial triradius t' and the absence of main­line C are high; of loops II and III, hypothenar patterns and axial delta t low. The alignment of the A mainline is longitudinal. Despite this, marked differences are noted between the present results and those of several studies of Andean and other populations which may be neither the result of poor sampling intensity nor genetic drift, but which may reflect the operation of certain selective agencies, as yet unknown.