BACKGROUND Xeroderma pigmentosum (XP) is an autosomal recessive disease caused by mutations in DNA repair genes. Clinical manifestations include extreme sensitivity to ultraviolet (UV) rays, freckle-like pigmentation, ocular abnormalities, and an increased risk of developing neoplasms in sun-exposed areas of the skin, mucous membranes, and eyes. This paper describes the clinical outcome of pegylated interferon alpha 2b (PEG-IFN-alpha-2b) subconjunctival injections and topical mitomycin C (MMC) in the treatment of ocular surface squamous neoplasia (OSSN) in patients with XP. CASE REPORT A series of 3 patients with histopathologically-proven biopsy specimens of XP-associated neoplasia of the eyelids and ocular surface underwent subconjunctival injections of PEG-IFN-alpha-2 band topical cycles of MMC. There was a noticeable decrease in the size and severity of ocular surface squamous neoplasia, with minimal adverse effects of flu-like symptoms with mild fever and generalized malaise. Transient mental depression was reported in 2 of our patients, and only 1 patient developed autoimmune diabetes mellitus, which required insulin therapy after the discontinuation of the PEG-IFN-alpha-2b. CONCLUSIONS The literature on the specifics of ocular care using PEG-IFN-alpha-2b for XP-associated OSSN is sparse. However, according to our clinical experience, the combination of PEG-IFN-alpha-2b subconjunctival injection and the topical cycles of MMC is a promising long-term medical therapy to minimize the development and recurrence of OSSN in XP patients.