Graves' ophthalmopathy (GO), the most frequent extrathyroidal manifestation of Graves' disease, is a disorder of autoimmune origin, the pathogenic mechanisms of which are still incompletely understood. Although GO is severe in only 3-5% of affected individuals, quality of life is severely impaired even in patients with mild GO. The role of radiotherapy in the management of GO is discussed controversially. However, recent randomized clinical trials have, with one exception, confirmed that orbital radiotherapy is an effective and safe therapeutic procedure for GO. This article describes the sequences, dosages and fractionation schemes as well as the risks and side effects of the radiotherapy.