Transantral decompression was performed bilaterally in 27 and unilaterally in 3 patients with endocrine exophthalmos of Graves' disease. In 28 patients there was an immediate reduction of proptosis and in about half of the patients in addition a marked decrease in chemosis and conjunctival injection indicating that these signs were mostly due to orbital vascular congestion. In one patient with exophthalmos of more than 2 years duration and progressive swelling of the eye muscles no response was observed. In another patient decompression did not reduce proptosis which, however, 4 months later responded to retrobulbar irradiation. In one further patient much more marked reduction of proptosis and disappearance of persistent periorbital swellings were obtained after glucocorticoid treatment given half a year after decompression. Postoperatively diplopia occurred in about half of the patients but corrective operations were required only in a quarter of the patients. Transantral decompression is an effective method for rapid treatment of progressive exophthalmos of Graves' disease. In patients with unilateral exophthalmos the asymmetry may be reversed after unilateral operation. The authors use decompression not only in the most severe cases (categories 5 and 6a-c according to the classification of the American Thyroid Association) but also in less severe cases (categories 2b-c and 3b-c) when there is a steady progression as a primary treatment possibly combined with other forms of therapy.