The 27-kDa human heat shock protein (hsp27) is dually regulated by both estrogen and heat shock treatment. Its function is obscure, but the high degree of homology to the lens alpha-crystallins and to the small heat shock proteins of Drosophila suggests that it may serve a structural function. There are at least three related human hsp27 sequences. To provide possible insight into the dual regulation of hsp27, we have determined the chromosomal location of all these and found them to be on separate chromosomes: 3, 9, and X.