Preformed tracheal tubes are used frequently in paediatric anaesthesia. A feature which contributes to their popularity is the belief that they can be positioned more reliably than conventional tracheal tubes because of their design. We studied a group of 40 patients in whom the incidence of bronchial intubation was 20%. The tube was too long in 32% of patients, although the tube size was appropriate for the child's age in all patients. The consequences and outcome of this complication are discussed. Copyright © 1991, Wiley Blackwell. All rights reserved