Polymorphism of 18 STR loci specific to the human Y chromosome (DYS19, DYS388, DYS389I, DYS389II, DYS390, DYS391, DYS392, DYS393, DYS426, DYS437, DYS438, DYS439, DYS460, GATA H4.1, DYS385 a/b, and YCAII a/b) was evaluated by means of a multiplex (octadecaplex) PCR reaction and capillary electrophoresis in a Polish population sample of 208 unrelated males. A total of 192 different haplotypes and 183 unique haplotypes were identified. The observed haplotype diversity was 0.998, while discrimination capacity was 92.3%. DYS389 was shown to be the most valuable in discrimination of similar haplotypes, whereas DYS388, DYS393, DYS426, and DYS438 did not affect the discrimination power of the multiplex.