The study aimed at development of a multiplex PCR system for amplification of three Y-chromosome STR loci: DYS390, DYS392 and DYS393, and its application in haplotype polymorphism analysis in the population of northern Poland. Due to interactions between originally published primers, a new DYS392 primer pair was proposed. In a population of 158 unrelated males, 28 different haplotypes could be observed, 12 of which were seen only once. The haplotype diversity is 0.805. Distribution of haplotypes of the studied loci is specific to the population of northern Poland and distinguishes it from compared West-European populations. To our knowledge, this is the first report on a Y-STR multiplex system that can be analysed on native polyacrylamide gels.