The spotted locus is responsible for several phenotypically distinguishable piebald patterns in cattle, including Hereford, or white face (SH), lineback (SP), and recessive spotting (s), in addition to nonspotted (S+). In a backcross mapping population, the S locus has been mapped by genetic linkage to bovine chromosome 6, between microsatellite markers BM4528 and EL03. This region corresponds comparatively to a region on mouse chromosome 5 which houses several coat color mutations, among which homology is possible with Hardy-Zuckerman 4 feline sarcoma viral oncogene homologue (Kit), patch (Ph), and rump white (Rw). Mutations at these loci resemble mutations at the bovine S locus in both phenotype and mode of inheritance. Data are presented which show genetic linkage between the bovine S locus and microsatellite markers on chromosome 6. Candidate genes for the bovine S locus are discussed.