Reproduced hyper variable segment I (HVS-I) sequences were obtained from mtDNA of 111 individuals from the medieval Carpathian Basin: 31 mtDNA profiles from Avars, 76 from Hungarian conquerors and four from the southern Hungarian-Slavic contact zone (see Supplementary Table S3). The mtDNA of 111 individuals was extracted at least twice per individual from different skeletal elements (tooth and femur or other long bones, Supplementary Table S1), the HVS-I fragments were reproduced in subsequent PCR and sequencing reactions, at least twice per DNA extract. The sequence results of these replicates, spanning HVS-I nucleotide positions (np) 16040–16400, typing individual selections of 14 coding region positions and two fragments of the HVS-II (np 29–254) confirm the haplotypes to be authentic. Of the 144 processed samples, 33 had no amplifiable DNA yield, or the sequences gave ambiguous haplotype results.