The photoreceptor outer segment and retinal pigment epithelium of vitamin E deficient rats given vitamin E were studied by electron microscopy. In rats fed a vitamin E deficient diet for more than 12 months, the photoreceptor outer segment did not regenerate after the administration of 400 mg of vitamin E. The retinal pigment epithelium was filled with lipofuscin granules and contained cytoplasmic organelles such as mitochondria, ribosomes and Golgi apparatus. The microvilli of the retinal pigment epithelium were long and in contact with the outer nuclear layer cells. The photoreceptor inner segment and nucleus had almost disappeared. In rats given 400 mg of vitamin E after vitamin E deficiency for 6 months, the photoreceptor outer segment showed no vesiculation and were increased in number. However, some retinal pigment epithelial cells still contained many lipofuscin granules. In conclusion, the photoreceptor outer segment and retinal pigment epithelium can be repaired in mild vitamin E deficiency by vitamin E administration, but vitamin E cannot reproduce the photoreceptor cells in nuclei of which have been broken by severe vitamin E deficiency.