A 74-year-old woman underwent right thoracotomy to remove a lung neoplasm. After general anesthesia had been induced, a no. 37 Bronchocath (Mallinkrodt) left endobronchial tube (TDL) was inserted. The TDL was initially positioned in the right mainstem bronchus and then had to be removed and repositioned in the left mainstem bronchus. It was not deemed necessary to use a fibrobronchoscope at this stage. During surgery the reduced minute expiratory volume and signs of pneumomediastinum made it necessary to perform tracheobronchoscopy. This led to the diagnosis of a rectilinear rupture of the left mainstem bronchus starting immediately below the carina, at the level of the pars membranacea and extending as far as the origin of the superior lobar bronchus. The left TDL was replaced by a similar right TDL and emergency left thoracotomy was performed following surgical repair of the damage. No problems of note occurred during the postoperative period. The patient did not present any of the predisposing risk factors for rupture of the tracheo-bronchial tree, except for slight fragility of tracheal respiratory mucosa. The anesthetist did not use fibrobronchoscopy or any devices to control the pressure level of TDL sleevs during the intubation and selection of the bronchus. These aids might have prevented the occurrence of a potentially fatal complication.