The diagnosis of esophageal rupture in balloon dilatation is usually made from clinical symptom of sharp chestpain, plain chest radiographs and esophagograms after dilataion. It has some problems; the pain is varied patientsto patients and bacterial flora in the mouth or esophagus can be mixed with the contrast media to flow into themediastinum during esophagography, to create mediastinitis. We could make the diagnosis of esophageal rupturewithout using contrast media by the observation of the presssure change in the balloon during dilatation. Aninfusion pump, trasducer and esophageal balloon were connected through multi-way connector,and the transducer ofthem was also connnected to an amplifier which was connected to a pressure monitor to record the balloon pressure.A balloon(20mm/3cm) inserted in the mid-thoracic esophagus under the fluroscopic control was inflated until theesophagus was ruptured. Balloon was distended by injecting air in 15 rabbits(A group), and by injecting dilutedcontrast medium in 15 rabbits (B group). The pressure decrease after esophageal rupture was ranged from 94 to 160mmHg(mean; 103) in a group and 340 to 1040 mmHg(mean; 537) in B group. The pressure curve of A group was smooth,regular and so accurate to make the diagnosis of esopahgeal rupture, whereas that of B group was irregular and notso accurate. In conclusion, our new method to make the diagnosis of esophageal rupture during balloon dilatationmay be useful in patients of esophageal stricture.