BACKGROUND: Double lumen endobronchial tube and single lumen tube with bronchial blocker are most frequently used tubes for one lung anesthesia. This study compared the double lumen endobronchial tube with the single lumen tube with bronchial blocker to determine whether there were objective advantages of one over the other during one lung anesthesia. METHODS: Sixty patients were randomly assigned to one of two groups. Thirty patients were intubated with a left-sided double lumen endobronchial tube, and thirty patients were intubated with a single lumen tube with bronchial blocker. Each group was subdivided into two groups with a person intubating (i,e, certified anesthesiologist or resident) to compare the easiness of intubation according to the type of tube. Fiberoptic flexible bronchoscope was used in all patients. The following were studied 1) time required to position each tube until satisfactory placement achieved, 2) frequency of malposition after initial placement with fiberoptic bronchoscopy, 3) surgical exposure ranked by surgeons blinded to type of tube used, 4) easiness of tracheobronchial toilet (TBT). RESULTS: 1) Statistically significant differences were observed in time required to place each tube by resident(double lumen tube 5.73+/- 0.48 min. versus single lumen tube with bronchial blocker 4.18+/-0.70 min (P<0.05) and in easiness of TBT (double lumen tube 18/30 versus single lumen tube with bronchial blocker 27/30) (P<0.05). 2) No differences were observed in time required to position each tube by anesthesiologist, the frequency of malposition and surgical exposure. CONCLUSIONS: Single lumen tube with bronchial blocker is better in easiness of intubation by resident and in easiness of TBT than double lumen endobronchial tube. But the selection of two tubes depends upon type of surgery and familiarity of each tube by the anesthesiologist.