To calculate the DNA-profile frequency, it is essential to know the allele distribution frequency in a given population. The study and determination of the allele frequencies of ten STR loci (SGM plus) in the Polish population served as a basis for assessing the effect of rare alleles on the statistical interpretation of DNA analysis results and their relation to the National Research Council Report recommendations. The statistical analysis we carried out showed that low-frequency alleles appear rarely in the multiplex STR profile, which means that their effect on the final frequency profile is not great. Frequency profiles calculated for the SGM Plus system with correction for rare alleles, and without correction, are never greater than c. 1.9 x 10^–11, which shows the great evidence value that the system provides in crime investigation.