The exophthalmost of Graves' disease remains a pathophysiologic and therapeutic puzzle. Its relation to thehyperthyroidism of Graves's disease is far clarified. It is a common clinical observation that exophthalmos doesnot often relate temporally with the onset of hyperthyroidism. Furthermore, exophthalmos may occure in patientswho have no evidence of thyroid disease. Pathologically, exophthalmos is characterized by marked lymphocyticinfiltration of the retro-orbital muscles, with edema and mucopolysaccharide deposition. Recently, cellularimmunity in response to retro-orbital antigens and abnormal humoral immunity are suggested for the pathogenesis ofexopthalmos. We experience 2 patients wtih hyperthyroidism and unilateral exophthalmos. The clinical andloboratory features of the patients are presented with review of articles, with emphasis on pathogenesis.