When iodized poppy seed oil 40 per cent was first advocated in intrabronchial instillation for the purpose of lung mapping, there seemed to us to be several theoretical objections. One of these was that a fibrosis of the lungs would be produced as a result of prolonged presence of an intrabronchial foreign body (iodized oil). Another was that bronchitis or bronchopneumonia would develop due to the transplantation of bacteria from the pharynx into the finer bronchioles by means of the oil. Long before we found experimentally that this second objection was theoretical only, we were convinced by reports of the clinics in which iodized oil 40 per cent had been taken up enthusiastically from the start that bronchitis and pneumonia did not follow its use. The validity of the first objection, however, seemed to us to be strengthened as we began to see patients a year or two after the