The human XRCC1 gene has been shown to be involved in DNA strand-break repair using the Chinese hamster ovary cell mutant EM9. The purpose of this study was to characterize the expression of Xrcc-1 to determine if there is tissue-specific expression and to provide a baseline of information for future studies that may involve altering Xrcc-1 expression in mice. Normal young adult male testis and enriched populations of pachytene spermatocytes and round spermatids displayed significantly higher levels of Xrcc-1 expression than other mouse tissues, although Xrcc-1 transcripts were found in low abundance in all tested tissues. Cultured mouse cell lines displayed levels of expression similar to male germ cells, which is a striking contrast to the levels of expression obtained in somatic tissues from the mouse. The relatively high levels of expression identified in male germ cells indicate Xrcc-1 may have an important role in male germ cell physiology.