The Hsc70t gene is a Hsp70 homolog gene expressed constitutively in spermatids in mice. This gene is linked to two heat-inducible Hsp 70 genes, Hsp 70.1 and Hsp 70.3, located in the MHC class III region. The syntenic region of human chromosome 6 contains the HSPA1B, HSPA1A, and HSPA1L genes. Here, we have isolated a HSPA1L cDNA clone from human testicular cells. The HSPA1L gene contained an intron 13 bp upstream of the initiating ATG, A similar genomic structure was found in the Hsc70t gene. The transcription initiation site of the Hsc70t gene was located at ca. 600 bp upstream of the heat-inducible Hsp70.3 gene, linked head-to-head. Sequence alignment of the mouse and human genes revealed that the human HSPA1L and HSPA1A genes were orthologous to the mouse Hsc70t and Hsp70.3 genes, respectively. Conserved sequence stretches observed in the 5' flanking region and the first exon of the spermatid-specific Hsp70 gene may be involved in regulation of the specific gene expression.