A genetic linkage map of rat chromosome 9 consisting of five loci including a new biochemical marker representing a genetic variation of the activity of the liver aldehyde oxidase, (Aox) was constructed. Linkage analysis of the five loci among 92 backcross progeny of (WKS/Iar x IS/Iar)F1 x WKS/Iar revealed significant linkages between these loci. Minimizing crossover frequency resulted in the best gene order: Aox-D9Mit4-Gls-Cryg-Tp53l1. The homologues of the Cryg, Gls, and Aox genes have been mapped on mouse chromosome 1 and human chromosome 2q. The present findings provide further evidence for the conservation of synteny among these regions of rat, mouse, and human chromosomes.