Lower respiratory tract secretions uncontaminated with oropharyngeal flora were obtained from the main bronchi and the trachea by a bronchofiberscopic technic for bacteriologic evaluation and compared with cultures from the throat. The reliability of this method for providing selective lower airway specimens was confirmed by in vivo and in vitro testing. Of 38 elderly patients (68 ± 13 years) with respiratory tract infections and 14 patients (53 ± 20 years) with noninfectious lung disorders, 35 harbored pathogens in their lower airways. In only half were the same bacteria present both in the main bronchi and upper respiratory tract, indicating the somewhat limited diagnosic value of cultures from expectorated sputum or throat swabs in these patients. Bronchofiberscopy offers an innocuous bedside technic for the bacteriologic evaluation of the lower respiratory tract and appears to be preferable to the transtracheal aspiration method because it provides collection of a selective bronchial specimen, visualization of the bronchial mucosa and secretions, and tracheobronchial toilet in patients with retained secretions. Supported in part by General Research Support Grant, PHS grant No. FR-05622–01and a grant from the Leo Rosner Foundation. Presented in part at the annual meeting of the American Thoracic Society, May 21–24, 1972