The development of a useful genetic map of the domestic dog would benefit by the inclusion of type I markers; coding genes that can connect the canine map to the homologous gene maps of other mammalian species. A group of 280 comparative anchor tagged sequences (CATS), and universal mammalian sequence tagged sites (UM-STS), were optimized for canine assessment. One hundred and five were screened for genetic polymorphism among nine canine breeds and three wild species of Canis in an attempt to promote gene mapping of comparative type I markers. Three categories of variation--size, restriction fragment length polymorphism (RFLP), and single-strand conformation polymorphism (SSCP)--were assessed. The data showed that 50% of the type I markers discriminate between species and 40% showed genetic variation among dog breeds. Although polymorphism incidence between nominated breeds for gene mapping is more limited than found for established reference pedigrees in other species, the concept and application of these CATS and UM-STS markers is useful in capturing the comparative information required for the full application and efficacy of the dog gene map.