Deafness is hereditary in at least eighty dog breeds. The gene for deafness is often linked to genes for pigmentation patterns, especially those that involve white in the coat such as the merle gene (seen in collie-type breeds and harlequin Great Danes, among others) and the piebald gene (seen in such breeds as Dalmatians, bull terriers, and English setters). Blue eyes are often associated with deafness, although they're not a definite sign that a dog is deaf or may carry a gene for deafness. The genetics of deafness in dogs is not yet fully understood, so in breeds in which it's common, breeders must be especially careful.

Congenital hearing loss usually develops when a puppy is only a few weeks old, possibly because of the absence of pigment-producing cells, called melanocytes, in the ear's blood vessels. Needless to say, no deaf dog should be bred, and breeders are advised not to repeat any breeding that produces deaf puppies.