One-lung anesthesia can be very helpful to the surgeon during operations on the lung, mediastinum, esophagus, and thoracic aorta The standard method for one-lung anesthesia uses a double-lumen tube (Carlens, Robertshaw, etc). However, these tubes are diffieult to place and may not remain in a correct position. In addition, the lumen of each channel is inevitably too smaU for proper ventilation and suctioning. We have designed a new device for one-lung anesthesia which overcomes these disadvantages. This new device, named SLT (single-lumen tube), was made by amoured wire tube, the proximal end of which was connected to the Rusch rubber tube. So, this tube is larger in diameter, available in various sizes and very economic. We intubated 25 cardiothoracic patients with SLT under the fiberoptic guidance (Group A), and the other 25 cardiothoracic patients were intubated with Bobertshaw double-lumen tube by the direct laryngoscopy (Group B). There were no significant differences in heart rate, blood pressure, PH, PaCO2, PaO2 BE, HCO3, SaO2 and ETCO2 between the two groups compared with induction, one-lung ventilation, and two-lung ventilation values.