Abstract: Msj‐1 gene encodes a DnaJ protein highly expressed in spermatids and spermatozoa of both rodents and amphibians. We isolated and characterized the msj‐1 gene in mice. A bioinformatic approach was then used to predict the putative promoter region, chromosomal localization, and its presence in the human genome. The analysis of msj‐1 genomic sequence revealed that msj‐1 is an intronless gene. Interestingly, two regions (A and B, separated by 10,682 bp) on human chromosome 2 having respectively 78% and 77% nucleotide identity with the murine msj‐1 coding region were identified. This suggests the existence of an msj‐1‐like gene also in humans.