Deafness is often diagnosed in different dog breeds and has been identified as a significant problem for breeders, owners and clinicians. The aetiology can be inherited or acquired, and a distinction must be made between sensorineural and conductive forms of deafness. This paper provides a brief overview of the varieties of findings in different dog breeds and in one breed in particular including prevalence, phenotypic and gender associations, histology, modes of inheritance and the number of contributing genes in congenital sensorineural deafness. We have also described molecular genetic approaches to canine hearing loss and discuss how comparative genomics could help reduce the prevalence of deafness in affected breeds leading to new insights into the molecular mechanisms of auditory function in both dogs and humans.