The alpha interferion has multiple properties including antiviral activity, Immunomdulating effect and antiproliferative effect of new vessels. In ophthalmic uses, the alpha interferion used to treat of corneal neovascularization, subretina neovascularization, angioma and neovascular glaucoma with systemic administration. But topical application seems to be higher in therapeutic effect at the site of action with fewer side effects than systemic use.We investigated the ocular permeability of topical I tagged-interferon alpha-2a, 3 million IU/ml. Eight pigmented rabbits were divided into two groups : intact corneal epithelium(Group A) and denuded corneal epithelium(Group B).There were no differences between 30 min and 60 min level after last installation.Cornea and aqueous humor of group B showed significantly higher concentration than those of group A(P<0.01). Highest concentration was detected in blood and lower levels were detected in aqueous, vitreous, conjunctiva, cornea, sclera and iris in the decreasing order in group B. Penetration rate of group B was 0.049%/ 0.1ml of aqueous and 0.00058%/mg of cornea. Because the penetration of interferion into posterior segment was little, the effect of topical interferion on posterior segment was insignificant but it may be beneficial in the treatment of anterior segment.Because topical interferion has hydrophilic character, the ocular penetration rate of interferion was little in normal rabbit’s cornea. Therefore an appropriate lipophilic vehicle was needed to improve the ocular penetration of interferion.Also punctual obstruction was beneficial to decrease the systemic concentration and reduce the systemic side effect of interferion.