A human cDNA probe was used to screen a panel of mouse-Chinese hamster somatic cell hybrids to determine the chromosomal location of the retinoblastoma susceptibility gene (Rb-1) in mouse. The Rb-1 gene mapped to mouse chromosome 14. Thus, the retinoblastoma susceptibility gene is syntenic with esterase 10 (the mouse homolog of human esterase D). The chromosomal assignment of the mouse Rb-1 gene was further confirmed by using the same probe to study mouse-rat microcell hybrids. Since the human retinoblastoma susceptibility gene (RB1) along with the gene for esterase D is on chromosome 13q14, these data indicate this linkage group is conserved in man and mouse.