Graves' ophthalmopathy (GO) is an autoimmune disorder of the orbit that is clinically relevant in 25-50% of patients with Graves' disease and 2% of patients with chronic thyroiditis. The age-adjusted annual incidence of clinically relevant GO is 16 per 100,000 population in women and 2.9 in men. At the onset of ophthalmopathy, 80-90% of patients have hyperthyroidism, with the rest having euthyroidism or hypothyroidism. The natural history of GO consists of two phases: an active inflammatory phase and a static phase. Anti-inflammatory therapy is indicated for the first phase of GO. Approximately 5% of patients experience late reactivation of GO. Asians appear to have less severe manifestations, with milder orbital edema, proptosis and muscle restriction. Genetic, anatomic and environmental factors influence the development of GO. Aging, thyroid dysfunction, thyroid stimulating hormone (TSH) receptor antibodies, smoking and radioiodine treatment for hyperthyroidism also influence the development and course of GO.