The 5382insC mutation in BRCA1 is a frequently reported mutation, being very prevalent in Central and Eastern Europe. This mutation was recurrently reported in Brazil and one case was reported Portugal, but not in Spain and other South-American countries,. We analyzed the haplotypic profile of seven Brazilian carriers of 5382insC to characterize a possible founder effect. The analyses indicated that mutation carriers shared an identical haplotype. The absence of this mutation in Spain, other South American countries, and sub-Saharan populations, as well as the patients' own ancestry, point to a significant Central or Eastern European contribution to the present genetic background of Brazilian population, different from the population structuring of remaining South American countries.