This bronchoscope differs from those normally used in the following ways: 1. In the endobronchial position the bronchoscope makes possible improvement in ventilation of the contralateral lung by increasing the area of the side-openings above the bifurcation. - 2. An inflatable cuff on the outer tube seals the bronchoscope against the trachea like a breathing tube. - 3. Jet-ventilation van be employed when the bronchoscope is open.