To determine chromosome positions for 10 mouse phospholipase C (PLC) genes, we typed the progeny of two sets of genetic crosses for inheritance of restriction enzyme polymorphisms of each PLC. Four mouse chromosomes, Chr 1, 11, 12, and 19, contained single PLC genes. Four PLC loci, Plcb1, Plcb2, Plcb4, and Plcg1, mapped to three sites on distal mouse Chr 2. Two PLC genes, Plcd1 and Plcg2, mapped to distinct sites on Chr 8. We mapped the human homologs of eight of these genes to six chromosomes by analysis of human x rodent somatic cell hybrids. The map locations of seven of these genes were consistent with previously defined regions of conserved synteny; Plcd1 defines a new region of homology between human Chr 3 and mouse Chr 8.