We evaluated the potential ocular surface toxicity of a recombinant interferon-alpha (IFN alpha) preparation on rabbit eyes. Topical application of this interferon (1 x 10(6) U/day in each eye) for 6 weeks produced no discernible conjunctival or corneal abnormalities on clinical, histopathologic, or ultrastructural evaluations. We believe that this recombinant IFN alpha preparation is not toxic to the ocular surface of rabbits.