The biological significance of autophagy in the metabolism of visual cells is discussed. In the process of autophagy, parts of the cytoplasm including cell organelles are surrounded by membranes. This formation is called an autophagic vacuole. Then, the contents of the vacuole are degraded by enzymes. Autophagy is a well known phenomenon occuring in various tissues. In visual cells, however, it was only recently first described by Remé and Young and Remé. Autophagy has been shown to occur in the visual cells of several normal species. The amount of autophagic activity follows a 24-hour rhythm, complementary to an overall protein synthesis. Thus, within a 24-hour period, one cycle of formation and degradation in visual cells is completed. Incubation of isolated retinas significantly increases the number of autophagic vacuoles in inner segments, indicating an adaptation of visual cells to changed metabolic conditions. It is assumed that changes in normal autophagic turnover may be an important factor in visual cell degenerative diseases, thus opening up a new field in retinal pathology.