Abstract: Sudden death in dogs due to cardiac disease is common. Many of these dogs die because of abnormal beats of the heart. Such diseases are likely inherited in the dog. Breeds at risk for such a cardiac death include the Doberman Pinscher, Boxer, Great Dane, Irish Wolfhound, Afgan Hound, Newfoundland and the German Shepherd Dog (GSD). To discover the genetic mutations that cause the diseases in each of these breeds will take many years of work. Research to identify the means of marking abnormal genes will help us to find the mutations. Even though the mutations will be different, research in one breed will help other breeds as we can use the gained information as we search the canine genome for the fatal inherited mistake. GSD have an inherited propensity for sudden death due to the occurrence of abnormal heart beats that develop primarily during sleep or with certain anesthetic agents. We have the needed pedigrees from GSD for our research. In this proposal we put forth a comprehensive plan to used stored samples from GSD that have died and their relatives so that we can identify potential abnormal genes and develop the markers for the most likely genes that could be involved in the disorder. Significant Accomplishments: Markers for many genes now developed. This will hopefully be of use to others studying either this or even unrelated diseases for which these may be candidate genes.