Somatostatin receptor scintigraphy with 111In-labeled octreotide proves to be a very sensitive diagnostic tool for evaluation of inflammative activity in endocrine ophthalmopathy (EO). The results of somatostatin receptor scintigraphy (SRS) in 40 patients with EO show a high orbital accumulation of 111In-octreotide in clinically active EO (4 h-median/orbit-brain-ratio: 12.6; controls 4 h-median: 5.8) Patients with clinically inactive EO (4 h-median: 7.1) show a similar orbital accumulation of radioactivity compared to controls. 5 patients with active orbital myositis also revealed an even higher orbital accumulation of radioactivity (4 h-median: 42.3). The diagnostic value of SRS lies in its ability to act as a measure of inflammation and can be useful as an activity parameter when planning therapeutic procedure as well as for EO follow-up. The results in patients with orbital myositis nevertheless do not permit a differential diagnosis with this method. The therapeutic value of 111In-octreotide in Graves' disease has yet to be established.