SummaryBACKGROUNDThe natural history of thyroid associated ophthalmopathy is poorly documented, although It is widely thought that many cases Improve spontaneously with time. This has Important Implications in the management of patients and is also a critical factor when assessing the effects of different treatments.OBJECTIVETo document the natural history of thyroid associated ophthalmopathy, 59 patients were studied longitudinally and the severity of eye disease documented at regular Intervals.METHODSFifty‐nine patients with thyroid associated ophthalmopathy who had not received Immunosuppressive or surgical treatment for their eye disease, were recruited from a combined thyroid‐eye clinic. They were assessed at presentation and at 3–6‐monthly Intervals for a median of 12 months. The eyes were assessed by separate and objective measurements relating to the status of the eyelids, cornea, extraocular muscles, proptosis and optic nerve function. In addition, a scoring system based on the above measurements was used to grade the overall severity of eye disease.RESULTSThirteen patients (22%) Improved substantially, 25 patients (42·4%) showed minor Improvement, 13 patients (22%) did not change, and 8 patients (13·5%) deteriorated progressively, to the extent that Immunosuppressive treatment was considered to be necessary.CONCLUSIONSA significant proportion of patients with thyroid associated ophthalmopathy (64·4% in the present series) Improve spontaneously so serial assessment plays an Important part in deciding which patients require Immunosuppressive treatment. These findings also support the view that clinical trials designed to test the efficacy of new treatments in thyroid associated ophthalmopathy should be scrupulously controlled to allow for the natural tendency towards