[en] The exophthalmos of Graves' disease remains a pathophysiologic and therapeutic puzzle. Its relation to the hyperthyroidism of Grave's disease is far from clarified. It is a common clinical observation that exophthalmos does not often relate temporally with the onset of hyperthyroidism. Furthermore, exophthalmos may occur in patients who have no evidence of thyroid disease. Pathologically, exophthalmos is characterized by marked lymphocytic infiltration of the retro-orbital muscles, with edema and mucopolysaccharide deposition. Recently, cellular immunity in response to retro-orbital antigens and abnormal humoral immunity are suggested for the pathogenesis of exophthalmos. We experienced 2 patients with hyperthyroidism and unilateral exophthalmos. The clinical and laboratory features of the patients are presented with review of articles, with emphasis on pathogenesis.