Transbronchial lung biopsy via the fiberoptic bronchoscope has been proposed for the diagnosis of diffuse lung diseases, particularly sarcoidosis. This study reports results in 167 patients. Lung parenchyma was obtained i 143 patients (85.6%). A cytologic or histologic picture compatible with the clinical presentation was found in 62.3% of all cases. Percentage of positive results was related to the study groups under consideration: 75.6% for diffuse interstitial infiltrates, 50.0% for chronic localized infiltrates, 52.0% fro solitary nodules, 73.5% for sarcoidosis (69.8% at stages 0 and I, 83.0% at stage II, 75.0% at stage III); and 54.4% for infectious pneumonitis. Complications included pneumothorax and bronchial hemorrhage, but were rare (4%) and minor. Because of its low morbidity and high diagnostic yield, fiberoptic transbronchial lung biopsy is the diagnostic tool of choice in various respiratory diseases, whether diffuse or localized.