Objective: To investigate whether orbital radiation offers effective and safe treatment for Graves ophthalmopathy. Methods: Medical literature databases were searched to identify all published reports relating to orbital radiation treatment for Graves ophthalmopathy. To be included in the technology assessment, reports had to provide original data, to report on a case series or uncontrolled trial of at least 100 subjects or a randomized clinical trial of any size, to focus on orbital radiation for the treatment of Graves ophthalmopathy, and to follow-up patients for at least 3 months. Abstracted data included study characteristics, patient characteristics, treatment response, and safety information. Results: Fourteen studies were included in the technology assessment: 5 observational studies and 9 randomized controlled trials. Three of the observational studies report on treatment response, with overall favorable outcomes for 40% to 97% of patients. Three of the observational studies provided intermediate-term safety data. The risk of definite radiation retinopathy is 1% to 2% within 10 years after treatment. Patients treated with orbital radiation did not have an increased risk of secondary malignancy or premature death. The 9 randomized trials were qualitatively heterogeneous. Patients with optic neuropathy generally were excluded from participating in the randomized trials. Three of the randomized trials were sham controlled. None of these studies showed that orbital radiation was more efficacious than sham irradiation for improving proptosis, lid fissure, or soft tissue changes such as eyelid swelling. Two of the 3 sham-controlled randomized trials demonstrated improved vertical range of motion in radiation-treated subjects compared with controls. Conclusions: Systematic review of the effect of orbital radiation on Graves ophthalmopathy is limited by the lack of standardization and variable quality of published reports. Extraocular motility impairment may improve with radiotherapy, although the evidence of a treatment effect is mixed in clinical trials. Future studies are needed to determine if a potentially beneficial motility effect results in improved patient function and quality of life. Level I evidence indicates that proptosis, eyelid retraction, and soft tissue changes do not improve with radiation treatment. The efficacy of orbital radiation for compressive optic neuropathy resulting from Graves ophthalmopathy has not been investigated in clinical trials and merits further study. Radiation retinopathy, although rare, is a risk of orbital radiation, even in patients without diabetes who receive appropriate radiation dose and delivery.