Regularly, STR results obtained with different PCR amplification kits are compared, for instance with old cases, when revisiting cold cases or when addressing cross-border crimes. It is known that differences in primer design for the same loci in different kits may give rise to null alleles or shifted alleles. In this study, the genotyping results of 2085 Dutch male samples were compared for six autosomal STR kits (Promega's PowerPlex (R) 16, ESX-16 and ESI-17 Systems, Qiagen's Investigator (R) ESSplex Kit and Applied Biosystems' AmpFlSTR (R) Identifiler and NGM PCR Amplification Kits). A total of 19 discordant autosomal genotyping results were obtained that were examined by sequence analysis using Roche-454 next generation sequencing and/or Sanger sequencing. A further 25 discordances were found and sequenced for the Amelogenin locus. The 24 samples showing the same primer binding site mutation at the Amelogenin locus were subjected to X-STR analysis in order to assess whether they could share a common origin, which appeared not to be the case. Based on the sequencing results, we set the final genotypes and determined the allele frequencies of 23 autosomal STRs for the Dutch reference database. (C) 2014 The Authors. Published by Elsevier Ireland Ltd. All rights reserved.