To evaluate the relationship between arterial and ent tidal carbon dioxide teneion, we use ETCO2cuffed tracheal tude. Twenty five patients were selected for the study. The anesthesia was induced by pentothal sodium 4-5mg/kg, succinylcholine 1-1.5mg/kg After intubation, anesthesia was maintained by halothane, nitrous oxide and oxygen. The patients were ventilated mechanically with tidal bolume 10 ml/kg and respiration rate 12/min When anesthesia was stabilized, end tidal cardon dioxide tension were measured at proximal and distal site of ETO2cuffed tracheal tube. The arterial blood sample were taken for arterial carbon dioxide tension from radial artery simultaneously. The results were as follows: 1) Both the end tidal carbon dioxide tension at proximal and distal sites of the tube showed close correlationship with arterial carbon dioxide tension 2) There was no statistical significant difference in carbon dioxide tension between proximal and distal site of ETCO2cuffed tracheal tube.