Copper toxicosis is an autosomal recessive disease (affected dogs must receive a gene from each parent) in which there is an accumulation of copper in the dogs body, resulting in severe liver disease. The Bedlington Terrier is one of the breeds most affected by this disease. Humans suffer from a similar heritable disease called Wilsons disease, and scientists have identified the gene in humans (the ATP7B gene) whose mutation causes Wilsons disease. Previous research at another institution had cast doubt on the idea that the same gene in dogs causes CT, but it had not been definitively ruled out. This project sought to determine whether the canine equivalent of this gene causes CT. While the research was not definitive, it eliminated from consideration the ATP7B gene as the site of the Bedlington Terrier mutation.