We have determined the chromosomal locations of the two cholecystokinin (CCK) receptor genes in the mouse. Genetic localization utilized an interspecific backcross panel formed from the cross (C57BL/6J x Mus spretus) F1 x Mus spretus. Genomic DNAs from 94 individuals in the backcross were analyzed by Southern hybridization with rat CCKA and CCKB receptor cDNA probes. Unique map positions were determined by haplotype analysis with 650 previously mapped loci in the mouse backcross. The CCKA receptor gene (Cckar) mapped to mouse Chromosome (Chr) 5, in tight linkage with the DNA marker D5Bir8. The CCKB receptor gene (Cckbr) mapped to mouse Chr 7, tightly linked to the beta-hemoglobin locus (Hbb). This localization places Cckbr in the same region as the mouse obesity mutation tubby (tub), which also maps near Hbb (2.4 +/- 1.4 cM). Since CCK can function as a satiety factor when administered to rodents, localization of Cckbr near the tub mutation identifies this receptor as a possible candidate gene for this obesity mutation.