A severe disorganization of the lattice arrangement of tapetal rods occurs in cats nutritionally deprived of taurine. This is the first reported example of a nutritionally related degeneration of tapetal cells. The tapetal cell degeneration, along with the previously noted photoreceptor degeneration in taurine-depleted cats, suggests that taurine plays a vital role in maintaining the structural integrity of some biological structures. The visual evoked potentials were severely reduced in taurine-depleted cats as were the electroretinogram responses, as previously noted, indicating that they are deficient in light processing. These results also emphasize the importance of dietary taurine for the maintenance of normal structure and function of the eye, at least in the cat.