The Hsp40 (heat shock protein with molecular size of approximately 40 kDa) is one of the mammalian homologues of bacterial DnaJ heat shock protein. We have isolated and characterized a genomic DNA clone encompassing the entire coding sequences of the human Hsp40 cDNA. The Hsp40 gene (HGMW-approved symbol HSPF1) is composed of three exons divided by two introns. The 5' region of the gene is highly GC rich, and there are multiple basal elements for transcription factors including typical heat shock elements. The Hsp40 gene has been assigned to chromosome 19 band p13.2 by in situ hybridization.