Aspiration of gastric content is always a threat in emergency operations. The consequences of pulmonary aspiration are connected with both the volume and the character of the material inhaled, but perhaps the most serious consequences result from the relative acidity of gastric secretions. Inhalation of materiaI with a pH less than 2.5 causes an immediate iatense bronchoconstriction, epithelial degeneration of the bronchi, pulmonary edema and hemorrhage. Once the aspiration of material from the stomach is thought to have occurred, the airway should be cleared as soon as possible and any aspirated material remaining in the oropharynx should be cleared by means of suction. This experimental study was carried out to assess the therapeutic effect of suction on pulmonary aspiration of hydrochloric acid and the changes in chest X-ray findings caused by aspiration of the acid. The condition of oxygenation of the animals were studied by blood gas analysis. In this experiment,24 rabbits weighing 1.8-2.2 kg were used and divided into 4 groups each group consisting of 6 rabbits. Group I: No suction after aspiration Group II: Immediate suction after aspiration Group III: Suction 5 seconds after aspiration Group IV: Suction 10 secoads after aspiration Each of the four groups in the state prior to aspiration served as a control. All experimental animals were anesthetized by intravenous injection of ketamine 75 mg/kg and HC1 (pH: l.0, 2 ml/kg) was instilled into the trachea through a tracheostomy tube while the animals were fixed in a head-up position. Suction was made 5 times vigorously through a tracheostomy tube using an electric suction apparatus in the suction groups. Spontaneous respiration was maintained in room air throughout the experiment. To see cehange in the findings of the lung, chest X-ray was taken 24 hours after the aspiration of HCL. The sample of arterial blood was taken from the femoral artery and analyzed for blood gas 5 minutes, 10 minutes, 30 minutes, 1 hour and 2 hours after the aspiration of HCl. The results were as follows:1) In all rabbits except one in group II, the findings of radioopacity was visible in the lungs 24 hours after the aspiration of HCL. 2) In the chest X-ray findings, group I revealed radioopacity in the area of 74.76±8.93% of the whole lung field, group II in the area of 9.13±5.84%, group III in the area of 40.67±15.89% and group IV in the area of 58.96±6.65%. 3) In blood gas analysis, PaO2 decreased to 52.2% of control at 5 minutes in all aspiration groups (P<0.01) and 2 hours later, the recovery of PaO2 values observed were 73.2% of the control in group I, 88.7% in group II, 82.7% in group II and 77.1% in group IV, The value of the PaCO2, was significantly decreased at 10 minutes, 30 minutes, 1 hour and 2 hours in group II(P<0.01) after aspiration but in the other groups, the changes were insignificant. The value of pH shown insignificant decrease in group I and group IV, and insignificant increase in group II and group III. From the above findings, the pulmonary changes after the aspiration of hydrochloric acid seemed not to be lessened by suction treatment after 10 seconds following aspiration of the acid.