Using fluorescent in situ hybridization (FISH) method, gene encoding the catalytic subunit of protein phosphatase type 1 beta (PPP1CB) in human and its corresponding gene in rat (PP1 delta) and mouse (dis2m2) were mapped to human 2p23, rat 6q21-q23, and mouse 12D, respectively. These results indicate that PPP1CB is a member of conserved syntenic group. It is shown that the genes encoding catalytic subunit of protein phosphatase type 1 family (PP1 alpha, PP1 beta, and PP1 gamma in human and those corresponding genes in rat and mouse), in spite of their high identity, are located to different chromosomes in these three species.