Infection with Epstein-Barr virus has been reported to have numerous systemic and ocular manifestations. In this study, a 38-year-old man with acute infectious mononucleosis was examined for a painless left red eye of three days' duration. The patient had a two-week history of fatigue, low-grade fever, sore throat, and lymphadenopathy. Serologic evaluation was indicative of an acute primary infection with Epstein-Barr virus. A large, salmon-colored, supranasal bulbar conjunctival mass was observed in the left eye. No associated conjunctivitis was present. Biopsy of the conjunctival lesion disclosed a dense leukocytic infiltrate, which consisted primarily of mature lymphocytes and plasma cells. Immunocytochemical evaluation of the tissue with monoclonal antisera disclosed Epstein-Barr latent membrane protein and nuclear protein 2 in a small fraction of the cells constituting the infiltrate. The conjunctival infiltrate resolved completely within one month, paralleling the regression of the patient's lymphadenopathy.