Ten patients with serious endocrine orbitopathy underwent radiation therapy of the retrobulbar orbital tissue. Between the 2nd and the 13th week preceding radiotherapy, exacerbation of the clinical symptoms had appeared in all the patients, and distinct symptoms of infiltrative tissular processes were seen beside bulbar protrusion. Of the cases, 5 suffered from marked extra-ocular myopathy, 6 from corneal lesions, and one patient had lost his visual faculty. Index numbers for the degree of the orbitopathy (4-11, average 6.7) were established in all cases, and a total focal dose amounting to maximally 1000 cGy for each retrobulbar target volume was administered in one series. The pituitary gland was not included in the radiation field. Indices for the degree of ophthalmopathy were reduced by at least 3 points (average 3.7). Swelling of soft tissue and bulbar protrusion were decreased primarily. No improvement of myopathy was obtained but aggravation also did not occur. Recurrences appeared in 4 patients, at the earliest 4 months, at the latest 24 months after the end of the therapy. The present findings have shown orbital irradiation as an effective method for the treatment of endocrine orbitopathy.