Old English Sheepdogs are affected with hereditary cerebellar degeneration (abiotrophy). The condition causes ataxia (incoordination) which begins late in life and is inherited as a recessive trait. While not necessarily fatal, ataxia results in frequent falls and injury and seriously compromises the dog’s quality of life. The delayed onset and recessive inheritance of this disease means that the trait can be widespread in the population and thus difficult to eliminate without a DNA test for carriers. We propose using a candidate gene approach to develop such a DNA test. We will develop DNA markers for the genes that are known to cause ataxia in humans and mice. We will then determine if any of these genes are responsible for the ataxia in Old English Sheepdogs. If the candidate gene approach is not successful, we will use any remaining resources to look for linkage between the ataxia and markers on the emerging canine genome map.