Fourteen new dinucleotide repeat polymorphisms specific for human chromosome 21 have been identified, mapped, and characterized. The average heterozygosity of all markers was 0.66. The average PIC value was 0.61. The markers were mapped by STS content mapping of YACs previously assigned to chromosome 21. The correlation of polymorphic genetic markers with substantially complete physical maps should facilitate the identification of loci of interest on chromosome 21.