The antibody Avastin is currently being used to treat different forms of cancer and eye diseases due to its antiangiogenic properties. Although Avastin has proven to be effective in patients with neovascular age-related macular degeneration, its exact method of action is unknown. In order to better understand its mechanism of action in the eye, we valuated the retinal penetration and distribution of Avastin and any effects on both Müller cells and microglia after intravitreal injection. The retinas were sectioned and labeled with antibodies to detect Avastin using a laser scanning confocal microscope. The resulting images indicated that Avastin penetrated the entire width of the retina after 24 hours. , which may explain the observed clinical effects of the antibody.