To establish a genotypic database for dinucleotide repeat marker loci in the Japanese population, we determined allelic frequencies of 12 such markers on chromosome 13 and compared them with data from Caucasians in the GDB archive. The average heterozygosity (79%) for the 12 loci was the same for the two populations. However, allelic distributions at two of the marker loci were quite different. These data will be useful for disease studies in the Japanese population that involve linkage or sibship-pair analyses, or association studies.