Retinal degeneration was observed in cats fed commerical dog food. The retinal degenerative lesions ranged in size from small areas of focal atrophy centered in the area centralis to generalized retinal atrophy. Blindness developed only in cats with generalized retinal atrophy. Analysis of the dog food diets, both dry and canned, revealed that taurine was absent or was present in very low concentrations when compared with control cat food diets. Plasma amino acid analysis also revealed taurine deficiency.