Levels of soluble IL-2 receptor in sera of 18 patients with sarcoidosis were measured by a sandwich ELISA method established by the authors and were found to be significantly higher than those in sera of normal subjects. Levels of soluble IL-2 receptor in sera of sarcoidosis cases of bilateral hilar lymphadenopathy (BHL) were significantly higher than those in sera of sarcoidosis cases without BHL. In patients with sarcoidosis, levels of soluble IL-2 receptor did not differ in relation to the presence or absence of ocular lesions, or in relation to positive or negative response to protein purified derivative of tuberculosis (PPD).