Conjunctival squamous cell carcinoma developed in a 51-year-old man 40 years after he had enucleation of his left eye because of an explosion injury. He had worn several ocular prostheses for more than 40 years. Recently he had noticed an increasing sanguineous conjunctival discharge, a foreign body sensation, and swelling of his left lower eyelid. Incisional biopsies of an underlying conjunctival mass revealed squamous cell carcinoma. His work history did not involve exposure to radiation, chemicals, or the sun. The authors concluded that squamous cell carcinoma in this case was caused by chronic irritation as the result of long-standing use of a poorly fitting ocular prosthesis.