The chromosomal locations of the rabbit genes for the α and β subunits of phosphorylase kinase (PHKA and PHKB) were determined by in situ hybridization using rabbit cDNA probes. Our results localize PHKA to the X chromosome at the proximal end of the long arm, near the centromere, and PHKB to the same location on chromosome 5. These assignments support previously reported homoeologies of rabbit and human chromosome