A 38-year-old woman from Antigua had compressive optic neuropathy of the right eye caused by orbital involvement with sinus histiocytosis. There was also nasal sinus involvement and massive cervical lymphadenopathy resulting in radiographic compression of the airway and carotid sheath. Because of the compressive optic neuropathy and threat to the airway and carotid perfusion, the patient underwent a 6-month chemotherapeutic regimen of cyclophosphamide, vincristine, and prednisone. After chemotherapy, the visual dysfunction resolved in correlation with diminution of the orbital mass, and marked regression of the cervical lymphadenopathy. This case demonstrates the potential efficacy of chemotherapy in the treatment of compressive optic neuropathy in cases of orbital sinus histiocytosis with massive lymphadenopathy.