A (GT)n repeat in intron 4 of the functional human HMG14 gene on chromosome 21 was used as polymorphic marker to map this gene relative to the genetic linkage map of human chromosome 21. Variation in the length of the (GT)n repeat was detected by electrophoresis on polyacrylamide gels of DNA amplified by the polymerase chain reaction using primers flanking the repeat. The observed heterozygosity of this polymorphism in 40 CEPH families was 58% with six different alleles. Linkage analysis localized the HMG14 gene close to the ETS2 gene and locus D21S3 in chromosomal band 21q22.3.