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Albino rats were exposed to fluorescent illumination for four to six months at an intensity which would not cause photocoagulation of the retina. Electron and light microscopic studies indicated that the retinas of these animals were irreversibly damaged and that the degeneration was specifically localized to the photoreceptor cells. Photoreceptors were not found in any of these retinas. Prolonged exposure to low intensity, visible light had no apparent effect on the bipolar neurons and ganglion cells or on their interconnections in the inner plexiform layer. Pigment epithelial cells survived the exposure and were unchanged except for extreme compaction of the apical villous processes in the retinal zone where the photoreceptors were located prior to their destruction. In some degenerated retinas the bipolar neurons were displaced along blood vessels extending from the inner ganglion cell layer to the outer retinal layers. Some of these blood vessels apparently formed anastomoses between the central retinal circulation and the choriocapillaries. The outer Miiller cell processes, which contained numerous lamellated and tubular structures, expanded to cover the area adjacent to the pigment epithelium and to form an outer limiting membrane, which was displaced in position in comparison with a normal retina.