This paper delivers population genetic data on Y-chromosomal short tandem repeat (STR) polymorphisms along with reports of unusual observations and casework. Population studies were carried out on the Y-specific STR polymorphisms DYS19, DYS385 I+II, DYS389 I+II, DYS390, DYS391, DYS392, and DYS393 in population samples from North India, Turkey, and Germany. In all three populations the vast majority of haplotypes was observed only once, especially in the Turkish group. Highly unusual cases are reported. In a German individual, we observed the variant allele DYS392*11.1, whereas a Turkish haplotype revealed a duplication at locus DYS19. Application of Y-chromosomal STR markers to forensic genetics was demonstrated in two cases: 1) a deficient paternity case, and 2) a father/son pair, where the Amelogenin primers failed to amplify the Y-homolog. In forensic genetics, Y-chromosomal STR polymorphisms are highly welcomed as an additional tool.