Phagocytosis of photoreceptor outer-segments through the retinal pigment epithelium (RPE) is a physiological important renewal process in the retina. Incomplete clearance of the photoreceptor outer-segment fragments cause photoreceptor degeneration and loss of vision. Recently new regulatory mechanisms of L-type Ca²⁺-channels in this phagocytosis process have been described (Karl et al. 2008, Cell Signal). Aim of this study was to investigate the functional relevance of these features. For in vivo measurement of retinal phagocytosis we labeled the outer segment protein rhodopsin in paraffin embedded retinal cross-sections of mice and quantified rhodopsin-positiv phagosoms in the RPE at different times of the day. Analyzing the photoreceptor outer-segments clearance we detected a increased activity in the morning. 30 minutes after light onset a peak number of phagosomes of 123 phagosomes per 100mm retina was detected compared with the afternoon, where we could survey about 4,52 phagosomes. In conclusion, phagocytosis shows a circadian regulation with a peak after onset of illumination in the morning. These investigations will provide a route towards a more detailed understanding of the functional role of Ca²⁺-channel in the regulation of phagocytosis.