The allele frequency and mutation rate in a Short Tandem Repeat locus, Y27 were studied in 247 unrelated Korean males using polymerase chain reaction followed by high-resolution polyacrylamide gel electrophoresis, a procedure called the amplification fragment length polymorphism technique. Six alleles were noted ranging from 190 bp to 210 bp. They existed as discrete bands with 4 bp discrepancy. Among which DY3(198 bp), DY4(202 bp) were common with the frequencies of 0.408, 0.356 respectively. Other alleles, DY1(190 bp, frequency 0.020), DY2(194 bp, frequency 0.121), DY5(206 bp, frequency 0.089), DY6(210 bp, frequency 0.004) were relatively uncommon. In a 78 subject father-son study with parenthood confirmed through other genetic studies, no case of mutation was noted. As the allele number was not as large as 6 and two alleles were dominant, the discrimination power in routine individual identification was thought to be low. But in selective cases such as father-son determination or sex determination, this locus could be a valuable genetic marker and we thought these results to be common for the Korean population. These results were also compared with that of other race.