A 54-year-old patient presented with a large, fleshy conjunctival lesion in the right eye that had been previously surgically removed in another centre. Diagnosis of Conjunctival intraepithelial neoplasia (CIN) was confirmed by conjunctival impression cytology. The tumor was treated with topical IFN-α-2β (1,000,000 IU/ (ml) adjuvant to surgery for chemoreduction purposes. One month after treatment, the lesion showed almost complete involution, therefore the treatment was continued up to 6 months, and the lesion showed full regression. The patient is currently under periodical follow-up by conjunctival impression cytology. We consider that topical IFN-α-2β can be used in CIN for chemoreduction and/ or curative purposes. We believe that conjunctival impression cytology is a useful and non-invasive method for diagnosis and follow-up in this condition.