Inherited BRCA2 mutations confer profound susceptibility to human breast and ovarian cancer. The rat and mouse Brca2 homologues share 58% and 59% identity (72% similarity), respectively, with the human BRCA2 protein. The Brca2 proteins also share a potential nuclear localization signal (human codons 3263-3269) and a highly conserved large carboxyl region (77% identity, 86% similarity between human and rodents) that may represent important functional domains. At least six of eight previously described BRC repeats have been highly conserved in rats and mice. Expression studies demonstrate an 11-12 Kb transcript with rodent tissue-specific patterns of expression consistent with human BRCA2. These results will facilitate studies of Brca2 function during normal and neoplastic development.