Double-lumen endobronchial tubes were placed "blindly" in 23 patients undergoing thoracotomy. Clinical criteria suggested satisfactory positioning in all cases; however, subsequent fibreoptic bronchoscopy revealed malposition in 48%. Bronchoscopic findings included the inability to view the bronchial cuff, narrowing of the bronchial lumen of the tube at the level of the cuff and herniation of the cuff over the carina. The potential hazards associated with these findings are discussed.