To evaluate the efficacy of transbronchial lung biopsy in the diagnosis of sarcoidosis, 26 consecutive patients with clinical features of sarcoidosis underwent this procedure during fiberoptic bronchoscopy. In 21, the biopsy revealed noncaseating granuloma and, in the remaining five, normal lung parenchyma. Subsequently, two of these five patients were found to have tuberculosis, one was confirmed as having sarcoidosis, and the fifth has not had further evaluation. Transbronchial lung biopsy was therefore successful in the histologic confirmation of sarcoidosis in 21 of 23 patients. The only complication was one 20 per cent pneumothorax, which resolved spontaneously. Because of its low morbidity rate, high diagnostic yield and specificity transbronchial lung biopsy is recommended as one of the initial procedures for obtaining histologic confirmation in patients with suspected sarcoidosis.