A total of 1,037 individuals living in five different sociogeographic regions of Brazil were studied in relation to 12 short tandem repeat polymorphisms. The objective was to assess the degree of European, African, and Amerindian contributions to their gene pools. Although most of the genetic variability was found within regions, significant differences were also observed between regions. The estimated relative proportions of the above-indicated continental contributions showed intermediate values between those obtained with uniparental (mtDNA, Y-chromosome) data, and a higher percentage of European heritage as compared to previous autosome results. A north–south trend of increasing European contribution was also found, in agreement with the history of the Brazilian population. Am. J. Hum. Biol. 15:824–834, 2003. © 2003 Wiley-Liss, Inc.