Rabbit ciliary body has been irradiated by accelerated proton beam. 24 animals have received on 20 and 40% of the total surface of ciliary body 45 and 60 Gy. We could confirm the very good precision of proton beam irradiation. No complication was noticed on slit lamp examination. The light microscope examination revealed haemorrhages, lymphocytes, plasma cells and histiocytes infiltration, late fibrosis and severe capillary alterations. The electron microscope examination showed a frank difference of radiosensitivity of the epithelial layers and a presumed partial rupture of the blood-aqueous barrier.