THIS TITLE implies an area of unusual flaccidity of a bronchus or portion of a bronchus in infancy, leading to collapse of the lumen, over-distension of the dependent portion of lung, possible displacement of the mediastinum, and probable secondary infection with recurrent pneumonia. The subject of this paper is an infant who died when 5 months of age of respiratory failure associated with segmental bronchomalacia. Retardation in growth and development of the left mainstem bronchus was basically responsible for this state of unusual softness of the bronchial wall. Recently, Gupta et al1 reported the first case of congenital bronchomalacia in childhood. The left mainstem bronchus of a 3-year-old boy was soft and collapsed. Bronchoscopic examination and bronchograms had shown a total collapse of the bronchus. There had been seven episodes of pneumonia confined to the left lung. On exploration, there was no recognizable external compression causing this obstruction. Instead,