We studied five population samples from Argentina, four drawn from Native American groups of the northeast region (Wichí, Pilagá, Toba, and Mbyá-Guaraní) and one from two small villages of the Córdoba province. In this study we report genotypes and allele frequencies of the 9.1-kb insertion-deletion polymorphism located on chromosome 22. The frequency of the deletion allele ranges from 0.276 in the Mbyá-Guaraní to 0.470 in the Pilagá. The coefficient of population differentiation is fairly low (F(ST) = 0.013), does not reflect any geographic or linguistic pattern, and seems to be more related to stochastic processes than to directional forces.