Craniomandibular osteopathy (CMO) is a painful bone disease that affects the quality of life of both the affected animals and their owners. It is most prevalent in the Cairn Terrier, West Highland White Terrier, and Scottish Terrier breeds. Although it is possible to identify carriers of the disease gene by test breeding, this method has many undesirable aspects to it and is not often used. The ultimate goal of this research is to develop a simple DNA-based test that will allow breeders to easily identify carrier and homozygous normal animals at any age. We have eliminated several candidate genes for this disease and we estimate that we have excluded 20-30 percent of the genome as containing the gene. We propose to complete the whole genome scan to locate linked markers to the disease gene. The linked marker(s) can then serve as the starting point for identification of the mutant gene and the development of a direct test for the mutation. This information will allow breeders to make informed decisions about which animals to use in their breeding programs. Simple breeding rules can then be applied to prevent the occurrence of affected animals and thus improve the lives of both animals and owner.