Human chromosome Y-specific short tandein repeat (Y-specific STR) markers have useful properties for forensic appplications However, there is a need to develop more Y-specific STR markers, because the discriminating power of each STR locus is liinited In the present study, we describe our results on six new Y-specific STR markers that were initially located using sequence database infomlation by Ayub et al and were named DYS434, DYS435, DYS436, DYS437. DYS438 and DYS439. Our stndies focused on the analysis of the DNA sequence for each allele at all six Y-specific STR loci in order to mlderstand their structures in the human genome and to construct human allelic ladders. which are necessary for forensic DNA typing in addition. the haplotype distribution for all six analyzed loci was studied in a Chinese Han population sample The results indicate that DYS434. DYS435, DYS436. DYS437, DYS438 and DYS439 are useful Y-specific STR markers for forensic sciences.