A 52-year-old man experienced chronic blepharoconjunctivitis of the right eye of the three years' duration that was unresponsive to medications. Conjunctival cytologic examinations suggested carcinoma and this was confirmed. However, only a full-thickness eyelid biopsy established that the tumor was a sebaceous carcinoma. We discuss the importance of considering this condition in all cases of unilateral, persistent, or recurrent eyelid inflammation resistant to the usual therapy; the diagnostic value of conjunctival scrapings and full-thickness lid biopsy; and the necessity of interpretation of the biopsy material by a pathologist experienced with, and alerted to look for, this neoplasm. Early recognition of sebaceous carcinoma followed by prompt adequate therapy should improve the survival of patients with this rare but malignant tumor.