Ten patients with primary hypothyroidism and ophthalmopathy are reported. None of the patients had previously received any form of therapy for thyrotoxicosis. In some patients hypothyroidism and exophthalmos presented simultaneously, but in others one clinical feature preceded the other by many years. Elevated titres of thyroid antibodies were found in 7 of the 10 patients and LATS was detected in 1 of the 10 patients. Increased 35S-sulphate uptake by the mouse Harderian gland technique occurred with serum from I of the 7 patients tested.