Wilson's disease, caused by a mutation in the ATP-ase 7B gene, is the only genetically characterised human disease with inhibition of biliary copper excretion and toxic copper accumulation in liver and occasionally brain. A similar copper toxicosis occurs in Bedlington terriers (CT) with liver damage only. Although CT has been associated with a defect in the COMMD1 gene (COMMD1 (del/del)), Bedlington terriers with CT and lacking this mutation are also recognised (non-COMMD1 (del/del)). A study was designed to identify any other gene polymorphisms associated with copper toxicity in Bedlington terriers employing genome wide association studies (GWAS) followed by deep sequencing of the candidate region. Blood for DNA analysis and liver for confirmation of the diagnosis was obtained from 30 non-COMMD1 (del/del) Bedlington terriers comprising equal numbers of CT-affected dogs and controls. DNA was initially subjected to GWAS screening and then further sequencing to target the putative mutant gene. The study has identified a significant disease association with a region on chromosome 37 containing identified SNP's which are highly significantly associated with non-COMMD1 (del/del) Bedlington terrier CT. This region contains the ABCA12 gene which bears a close functional relationship to ATP-ase 7B responsible for Wilson's disease in man.