We used in situ hybridization techniques to assign the human c-rel locus to the centromere-proximal portion of the short arm of chromosome 2 (2cent-2p13). We also determined the chromosomal location of c-rel sequences in the domestic cat and the laboratory mouse by using a human c-rel fragment to screen panels of rodent X cat and hamster X mouse somatic cell hybrid DNAs. The c-rel locus apparently maintains similar syntenic relationships with other known genetic markers in the human and cat, but displays different linkage relationships in the mouse.