The human mandibles belonging to Uruguayan population present some anatomic differences with those belonging to Brazilian population. This appears to be determined by racial and ethnic characteristics of each country. This study examined the morphological characteristics of 100 Uruguayan mandibles and compared them with similar number of Brazilian bones, using thirteen measurements stipulated by Humphrey et al. (1999). The significant variations in mean values were calculated by Mann-Whitney test (alpha=5%). Expressive discrepancies were observed between the two populations regarding some of analyzed dimensions. The Uruguayan mandibles showed higher values in almost all measurements when compared to the Brazilian ones, except for the mandibular symphysis height, which was lightly higher in Brazilian mandibles. Differences were observed in notch and ramus height, mandibular length, mandibular width, symphysis height and bicoronoid width. 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