Graves' ophthalmopathy is frequently a diagnostic and therapeutic dilemma for practicing ophthalmologists. We have reviewed the clinical immunology of this disorder with regard to clinical manifestations, humoral immunity, and cellular immunity. Special emphasis with applicable clinical and laboratory data is given to the hypothesis that Graves' thyrotoxicosis and ophthalmopathy may be frequently associated diseases rather than disorders caused by a common pathogenetic mechanism. Dysthyroidism may be the substrate for the development of the ophthalmopathy, but the two disorders probably are caused by different immunopathogenetic mechanisms.