A male sample of 135 African descendents from the Rio de Janeiro population were typed for the 12 Y-chromosome short tandem repeat (STR) loci included in the PowerPlex Y System. A high haplotype diversity was observed (0.9971), with 91% of haplotypes being unique, demonstrating the usefulness and informative power of this Y-STR set in male lineage identification. Samples with shared haplotypes were additionally typed with the Yfiler kit, which includes five extra markers. The haplotype diversity when using the 17-Yfiler loci increased to (0.9998) with 97% unique haplotypes. The same set of Y-STRs was also typed in 135 father/son pairs and three single-step mutations were observed one at DYS19 and two at DYS385. Genetic distance analysis showed highly significant differences in all pairwise comparisons between this sample of African descendents and the general population from Rio de Janeiro, as well as with Iberian and African samples from Portugal, Mozambique, Angola and Equatorial Guinea. Comparisons with samples from other regions in Brazil showed that heterogeneity does exist, indicating that a Y-haplotype database for the whole country should take into account the population sub-structure. Moreover, a strong European influence was detected, and thus, a Y-chromosome STR profile proves a rather poor indicator for the ethnic origin of an individual in Rio de Janeiro.