We have molecularly cloned and sequenced the mouse counterpart of the human repair gene XPG/ERCC5 cDNA. The mouse xpg cDNA had a single long open reading frame predicted to encode 1170 amino acid residues (predicted M(r) of 130,753). Northern blot analysis has been carried out to determine the size and tissue transcription specificity of the mouse xpg mRNA. The xpg gene expressed one species of transcript with 4.3 kb at similar levels in five mouse tissues examined. We have determined the chromosomal location of the xpg gene by both in situ hybridization and molecular linkage analysis. The xpg gene was localized at 2.3 cM proximal to the microsatellite locus D1Mit18 on the R-positive B band of mouse chromosome 1. By in situ hybridization with the mouse xpg probe, the rat homolog of the mouse xpg was localized on q22.3 band of rat chromosome 9, which has been known to have a conserved linkage homology to mouse chromosome 1. In the case of human, the XPG/ERCC5 gene has been reported to be assigned to human chromosome 13q32.3-q33.1, where any conserved linkage homology to mouse chromosome 1 has not been found so far. Thus, these results show new regions of conserved linkage homology among mouse chromosome 1, rat chromosome 9, and human chromosome 13q.