Since Sicard and Forestier first described a practical method of bronchography in 1922 (17), there have been relatively few refinements in the technic. The use of fluoroscopy and spot films, exposures in multiple projections, limitation of the amount of oil injected so as to avoid alveolar flooding, and postural drainage or suction of secretions from the discharging lung have all been recommended and incorporated into the bronchographic procedure. In spite of these advances, bronchograms are at times unsatisfactory. The limiting factors, no matter how exhaustive the effort, are (a) spread of the opaque material into the alveoli because of inability to control the cough reflex (an anesthetic failure) and (b) the incomplete opacification of some of the major or segmental bronchi for mechanical reasons. The first factor may be controlled by a careful and experienced topical anesthetist. The effect of the second factor may be partially eliminated by the use of films obtained one-half hour after the initial examination. In the fall of 1948, we obtained a bronchogram on a 58-year-old man with a history of cough, productive of a moderate amount of sputum, for many years. The left upper and left lower lobes were nicely delineated, but the lingula was incompletely filled. We were thus unable to exclude lingular bronchiectasis. Because the roentgenograms were not of optimal technical quality, more films were obtained. During the interval of about forty-five minutes between the first and second examinations, no additional Lipiodol was administered. On the delayed films, much alveolarization of the medium had occurred and some had obviously been expectorated; the lingular branches were now clearly visible, however, and bronchiectasis could be excluded. On the basis of this chance observation, an investigation of the value of delayed films in bronchography was initiated, and has continued until the present. The results of this investigation, embodied in an analysis of 100 consecutive bronchographic examinations performed between November 1948 and August 1951 in which delayed films were obtained, constitute the basis of this report. In 1929, Jacobaeus, Selander, and Westermark reported attempts to evaluate the “expectoration time” of intrabronchial Lipiodol (9). As part of their investigation, they obtained serial exposures over a twenty-four-hour period in some cases, although they made no mention of these being of diagnostic value. Similarly, Sicard and Forestier obtained sequential films over a period of months, in an effort to determine the time of disappearance of Lipiodol from the lung (17, 18). Fariñas utilized serial bronchography with spot films in some classical studies of the bronchial tree in pulmonary disease (5, 6).