OBJECTIVE: To evaluate the role of combined subconjunctival and topical interferon alfa-2b (IFN alpha 2b) in the treatment of conjunctival and corneal intraepithelial neoplasia (CIN). DESIGN: Noncomparative case series. PARTICIPANTS: Six patients with histologically proven CIN or recurrences of histologically proven CIN were studied prospectively. INTERVENTION: Patients were given a single subconjunctival/perilesional injection of recombinant IFN alpha 2b (Schering Plough, Kenilworth, NJ) 3 million international units (IU) in 0.5 ml and then started receiving topical interferon drops (1 million U/ml) four times a day. Patients were followed weekly until complete resolution of the tumor. After 1 week, patients with minimal response while receiving topical therapy were retreated with perilesional injections three times a week until resolution. Patients received topical interferon drops for a month after clinical resolution of the lesion. MAIN OUTCOME MEASURES: Patients were followed clinically and photographically for evidence of tumor resolution. RESULTS: The authors present a series of six patients who were treated successfully with a combination of subconjunctival/perilesional and topical IFN alpha 2b. All six patients had complete clinical resolution of the CIN lesion within 6 weeks of initiation of treatment. In the time of follow-up (average, 7.2 months; range, 2-11 months), there have been no treatment failures or recurrences. CONCLUSION: IFN alpha 2b may be a viable medical alternative to surgical excision for primary or recurrent CIN.