Idiopathic epilepsy affects over 30 different AKC dog breeds and was identified as the top canine health issue in the 2001 AKC/CHF Parent Club Survey. Preliminary studies in the Belgian Tervuren and Sheepdog indicate that although this is a heritable disorder governed by many genes, there exists a single gene of very large effect on the incidence of epilepsy. The epileptic condition influenced by this particular gene is inherited as an autosomal recessive. Preliminary data in our laboratory, derived from screening the DNA of affected dogs, identified a chromosomal region appearing to be associated with epilepsy. The specific objective of this project is to refine this initial association to a very discrete region of the DNA in order to ultimately develop a genetic marker associated with epilepsy. Such a genetic marker will permit the identification of carriers of epilepsy in Belgian Tervuren and Belgian Sheepdogs, and possibly other breeds, prior to breeding with the end result that breeders can make informed, health-based breeding decisions.