Short trachea results from reduction in number of tracheal cartilage rings to 15 or fewer from normal mean of 17 rings in infants. In a review of radiologic and pathologic data, the thoracic vertebral level of tracheal bifurcation as seen in anteroposterior chest radiographs of infants with congenital malformations, cardiovascular anomalies, and skeletal dysplasias, was compared with numbers of tracheal cartilage rings demonstrated in postmortem specimens. Increased frequency of short trachea was seen in patients with DiGeorge anomaly (77%), skeletal dysplasias (55%), brevicollis (57%), diaplacental rubella (40%), and patients with congenital heart disease who did not have DiGeorge anomaly (36%, with range 25-83% for different types, the highest, 83%, being interrupted aortic arch). Preintubation high kilovoltage chest radiographs to establish the level of tracheal bifurcation in patients with increased risk of short trachea can be helpful in avoiding bronchial intubation and its complications. Postintubation chest films to assure the level of the endotracheal tube tip should be considered for such patients. Growth in length of the trachea with age is accomplished both by increase in size of tracheal cartilage rings and interring membranes, and by increase in ring number.