The objective of the investigation was the calculation of biostatistical indices and parameters of medicolegal usefulness and extension of the knowledge on the genetic structure of the population in view of its historical background and ethnic composition. Polymorphism of Y-STR loci was determined in population samples including the total of 718 males of Polish nationality and belonging to the minorities of Byelorussians, Lithuanians, Polish Tatars and the religious minority of the Old Believers. Statistical analysis of genetic polymorphisms indicated their usefulness in characterizing populations and ethnic groups. The variations in haplotype distribution in northeastern Polish populations should be taken into consideration while evaluating probability of genetic profile matching in medicolegal expert opinions.