The human ninjurin gene was isolated from a cDNA library enriched for transcripts from band 9q22. A 1.2-kb message was detected for ninjurin in all human tissues studied. The full-length sequence codes for a putative 152-amino-acid protein with 89% identity to the rat ninjurin protein. The mouse homologue was isolated and showed 98% amino acid identity to the rat protein. Mapping by FISH localized mouse ninjurin to mouse chromosome 13, a region that shows synteny with human chromosome 9q22. Genomic characterization of the human gene revealed four exons covering less than 10 kb. The map position of the human gene is between the genetic markers D9S196 and D9S197 on human chromosome band 9q22. This places the gene within the candidate regions for the degenerative neurological disorder hereditary sensory neuropathy type I and the cancer predisposition syndrome multiple self-healing squamous epitheliomata.