SUMMARY Dogs fed purified diets developed retinopathy consistently when the nutrition was deficient in vitamin E. Deleting dl-methionine along with vitamin E and selenium (group 3 dogs) varied the development minimally. Supplementation of vitamin E to a selenium-deficient diet (group 1 dogs) protected the retina from changes. Ethoxyquin added to a diet deficient in vitamin E, but supplemented with National Research Council levels of selenium or 10 times the National Research Council levels, induced no beneficial recognizable changes in the retinopathy. The characteristic retinopathy was ophthalmoscopically visible as early as 3 months (group 2 to 9 dogs). Typical lesions developed first in the central, outer layers and progressed slowly toward the periphery. The tapetal retina was more extensively involved, showing a color change and mottling. Microscopically, a yellow autofluorescent pigment accumulated in large amounts within the retinal epithelium. Later stages of retinopathy showed this pigment was present in migrating cells in all the retinal layers. The early disappearance of a recordable electroretinogram, night blindness, and eventual severe day visual impairment makes this retinopathy similar to some aspects of degenerations described for persons and pure breed dogs.