Short tandem repeat (STR) markers DXS6801 (GATA41B11), DXS6809 (GATA69B129) and DXS6789 (GATA31F01) are located in a 3-Mb region on human chromosome Xq21, spanning approximately 3-6 cM. Theoretically, this cluster could give rise to 1,144 different haplotypes in the German population. In fact, genotyping of 806 males revealed the presence of 207 different haplotypes. Since the three STRs have been shown to be in strong linkage disequilibrium (LD), haplotype frequencies cannot be computed on the basis of single locus allele frequencies alone, but have to be estimated directly instead. In this work, we present data on linkage, haplotype frequencies and LD in the German population. To highlight the potential of the STR cluster for forensic analysis, we also report two examples of its successful application in pedigree-based kinship testing.