One lung ventilation (OLV) is required during thoracic procedures such as lung and esophagus surgery. three technique can be employed. (1) placement of a double-lumen bronchial tube (DLT); (2) use of a single-lumen tracheal tube (SLT) in conjunction with a bronchial blocker; (3) insertion of a conventional SLT into a main bronchus. Flexible fiberoptic intubation with SLT is well established technique for anticipated or unexpected difficult intubation. But, little is known about flexible fiberoptic intubation with DLT.