BACKGROUND The non-Hodgkin's lymphomas (NHL) are a group of neoplasms characterized by proliferation of malignant lymphocytes. Patients with NHL have a wide variety of presenting signs and symptoms, depending largely on the site of involvement and aggressiveness of the disease. Many organs in the body may be affected, including the eye and orbit. METHODS A 47-year-old male with a 3-year history of stage IV non-Hodgkin's lymphoma who had undergone recent monoclonal antibody therapy presented with a complaint of blur in the left eye with occasional diplopia. Significant ocular findings of the left eye included ptosis, mild proptosis, increased intraocular pressure, and choroidal folds. Magnetic resonance imaging of the orbit revealed an orbital lymphoma that completely resolved after 2400 rads of external beam irradiation therapy. Eight months later, the patient developed a secondary radiation retinopathy. CONCLUSIONS The prevalence of NHL is on the rise, and orbital involvement may occur at any time during the course of the disease. The standard treatment for non-Hodgkin's orbital lymphoma is external beam irradiation therapy, although the optimal dose for obtaining local tumor control without complications remains to be determined. Non-Hodgkin's lymphoma, orbital lymphoma, and various treatment options are discussed.