80 patients in three different institutions underwent transbronchial lung biopsy (TBB) through a fiberoptic bronchoscope to confirm the diagnosis of sarcoidosis. A positive tissue diagnosis was obtained in 50 (75%) patients. The diagnostic yields in radiographic stage I, stage II and stage II sarcoidosis were 55% (12 of 22), 80% (33 of 41), and 82% (14 of 17), respectively. When the results in patients with stage I sarcoidosis were reviewed in conjunction with abnormalities on pulmonary function studies only reduced functional residual capacity (FRC) was found to be associated with increased diagnostic yield (80%) on TBB. We conclude that except for patients with radiographic stage I disease and normal FRC, TBB is the procedure of choice in patients with sarcoidosis when readily accessible extrathoracic abnormalities are not present.