During the course of development of a modified (hydrophilic) form of Technegas, we were testing its properties on normal volunteers. The delivery mechanism for the inhalation manoevre had not been perfected, and one volunteer inhaled some rather large water droplets containing the Technegas particles. Twelve frames were collected over a period of 76 minutes taking four frames of four minutes, followed by eight frames of eight minutes. The resulting animated image sequence demonstrates the mucociliary escalator very clearly. The 'waving effect' at the upper end of the trachea is due to the subject turning his head from time to time to view the screen! Note the activity in the stomach as it is cleared from the lung, and the activity remaining in the peripheral portion of the lung where the activity has penetrated below the escalator which finishes at the 16th division of the bronchial tree.