(1959) found that an angulated catheter entered the left main bronchus through a tracheostomy tube far more readily than a straight catheter. Straight plastic catheters seldom entered the left bronchus regardless of the patient's head position (Kirimli et al., 1970). Even in infants, in whom the left and right main bronchi diverge from the trachea at almost equal angles, Bush (1963) observed that a straight catheter entered the right main bronchus far more commonly than the left. Haberman et al. (1973) have developed some practical guidelines that maximise the change of aspirating the left main bronchus. They recommended the use of angletipped catheters that had been packed straight rather than coiled, and that orotracheal rather than nasotracheal tubes be used. They also suggested that the patient's head should be turned to the right during catheter insertion. In 24 patients they had a 46% success rate in entering the left main bronchus, their successes increasing to over 60% in those patients with tracheostomies.We have used many of the guidelines suggested by Haberman et al. (1973) for catheterising the left main bronchus in a large number of patients. Our success rate was similar to that in previous studies and our experience has encouraged us to propose a further recommendation related to the length of catheters. Material and methodsForty-one patients in the Respiratory Intensive Care Unit were studied, 15 with tracheostomies and 26 with orotracheal tubes. The catheters were washed through with a radio-opaque solution, Lipiodol-Lafay (Denver Laboratories (Canada Limited)) for visualisation on the chest film. A total of 40 insertions was made on each group of patients, 20 with straight catheters and 20 with angled catheters.Intensive care unit nurses performed the aspirations. Specific attempts were made to place the catheter in the left main bronchus using catheter manipulation. In view of the minimal improvement reported by Haberman when turning the head to the contralateral side, this procedure was not followed. Initially the catheter was advanced until a resistance was met. A chest radiograph was then taken to determine the position of the catheter. All patients tolerated the procedure well.