PURPOSE: To study the effect of topical mitomycin C on conjunctival squamous neoplasia. METHODS: Three patients with recurrent conjunctival epithelial neoplasia were treated with topical mitomycin C 0.04-%. RESULTS: Six to 9 months after treatment, no patient had clinical evidence of tumor recurrence. Conjunctival biopsy in two patients and cytology in one patient showed no evidence of tumor 1 to 4 months after treatment. One patient required short-term treatment for corneal edema and epithelial toxicity. CONCLUSION: Topical mitomycin C caused tumor regression without recurrence for 6 to 9 months after treatment.