The human amylase gene cluster includes a (CA)n repeat sequence immediately upstream of the gamma-actin pseudogene associated with the AMY2B gene. Analysis of this (CA)n repeat by PCR amplification of genomic DNA from the 40 families of the Centre d'Etude du Polymorphisme Humain (CEPH) reference panel revealed extensive polymorphism. A total of six alleles with (CA)n lengths of 16-21 repeats were found. The average heterozygosity for this polymorphism was 0.70. Multipoint linkage analysis showed that the amylase gene cluster is located distal to the nerve growth factor beta-subunit gene (NGFB) and is within 1 cM of the anonymous locus D1S10. The amylase (CA)n repeat provides a convenient marker for both the physical and the genetic maps of human chromosome 1p.