Sixty-five patients with lymphoproliferative disease of the orbit were treated at the Joint Radiation Oncology Center of the University of Pittsburgh. An analysis of these patients was stratified by their initial tumor histopathology: benign lymphoid hyperplasia (BLH) in 28, malignant lymphoma (ML) in 20, and lymphoid infiltrate of indeterminate histology (IH) in 17. The median follow-up was 42 months. Radiation treatment was efficacious in all three groups of patients. The actuarial local recurrence-free survival rate is 84%. Treatment programs usually consisted of 20 to 30 Gy delivered in 10 to 15 fractions. ML patients had significantly lower overall and disease-specific survival rates than IH and BLH patient (p less than or equal to 0.02). BLH patients had a significantly lower local recurrence-free survival than patients with IH and BLH (p = 0.03). There was no significant difference between the three groups of patients with regard to the subsequent development of systemic lymphoma. There were no significant differences in local (16%) or systemic (36%) relapse between patients irradiated with less than 30 Gy or greater than or equal to 30 Gy. Cataracts were detected in 46% of the patients treated with anterior-posterior fields, but none were detected in those treated with other techniques. The results of this study emphasize the importance of long-term follow-up and careful treatment planning for patients with lymphoproliferative diseases of the orbit.