BACKGROUND: Sarcoidosis, uncommon in Korea, has variable clinical course, ranging from benign self-limited recovery to life-long disability regardless of corticosteroid therapy. The purpose of this st udy is to observe the clinical course of untreated sarcoidosis. METHODS: Twenty four patients who were confirmed as sarcoidosis by tissue diagnosis were included. For average 12month follow-up periods, subjective symptoms, radiologic findings, and parameters of pulmonary function test(FVC, FEV1, DLco) were evaluated every 3months compared between corticosteroid treated (n=5) and non-treated (n=19) patients. 'Deterioration' was defined if patients met more than one of followings (1) decrement in any parameters of pulmonary function test (2) worsening in the degree of dyspnea (3) increase in radiologic extents, and (4) newly developed extrapulmonary sarcoidosis. 'Stable' was defined as no significant interval changes in every parameters. 'Improvement' was defined as decrement of extension of the radiologic lesions without deterioration. RESULTS: Among 19 untreated sarcoidosis patient, one deteriorated, 14 improved (13 of them showed complete resolution in radiology), and 4 were remained stable. On the other hand, five corticosteroid treated patients, uveitis was developed in one, 2 improved, and 2 remained stable. CONCLUSION: These findings suggest that patient with sarcoidosis, especially those without serious extrapulmonary disease, has stable clinical course and would not need corticosteroid therapy.