The evaluation of the short tandem repeat (STR) markers DXS10079, DXS10074 and DXS10075 was amended to establish a STR cluster spanning a genetic distance<1 cM. These three STRs are located within a 280-kb region at Xq12 and provide stable haplotypes useful for solving complex kinship cases. Theoretically, this cluster could give rise to 2,548 different haplotypes in the German population and the genotyping of 781 men revealed the presence of 172 haplotypes. Since the three STRs were shown to be in strong linkage disequilibrium (LD), haplotype frequencies cannot be computed on the basis of a single locus allele frequency alone but have to be estimated directly. Here, we present data on linkage, haplotype frequencies and LD in a German population. Further clusters from other regions of the X chromosome will be published in the future to cover the chromosome with a well-structured network of highly informative sites.