Progressive Retinal Atrophy (PRA) is an inherited disease of the retina (the “film in the camera”) in dogs, in which the rod cells in the retina are programmed to die. PRA occurs in both eyes simultaneously and is nonpainful. There are many different types of inherited retinal degenerative diseases in purebred dogs, and discussing these are beyond the scope of this article. PRA occurs in most breeds of dogs and also occurs in mixed breeds. It is recessively inherited in all breeds studied, with the following exceptions: PRA is dominantly inherited in Old English Mastiffs and Bullmastiffs, and is sex-linked and found primarily in male dogs in Siberian Husky and Samoyed breeds.