Three African populations were genetically studied through a decaplex X chromosome short tandem repeat (STR) system, which includes the following loci: DXS8378, DXS9898, DXS8377, HPRTB, GATA172D05, DXS7423, DXS6809, DXS7132, DXS101 and DXS6789. A total of 237 unrelated male individuals from Angola, Mozambique and Uganda were typed. DXS8377 revealed to be the most polymorphic marker and in contrast, locus DXS7423 was the least informative in Angola and Mozambique and DXS8378 in Uganda. No significant associations between alleles of any pair of loci were found in these three population groups. The overall mean exclusion chances for the 10-plex in parentage testing, when both mother and daughter are investigated are above 1 in 4.2 million being the highest in Mozambique (1 in 5.3 million); in duos these values are approximately 1 in 60 thousand. Concerning the overall power of discrimination, this decaplex can discriminate 1 in nearly 41 million Ugandan men and 1 in around 30 million Angolan and Mozambican men; raising an order of magnitude of over 13 digits in all population groups for women. All these parameters demonstrate the potential of this decaplex for parentage testing as well as for identification purposes.