BACKGROUND: Many investigations were done about pulmonary protection in lung transplantation which is the most effective treatment of end-stage pulmonary disease. The objective of this study is to verify the effect of prostacyclin on the ischemia-reperfusion injury in terms of the change of arterial blood gas (ABGA), pulmonary vascular resistance (PVR) and pulmonary water content. METHODS: In twelve mongrel dogs weighing approximately 20 kg, double-lumen endotracheal tube was intubated and Swan-Ganz catheter was inserted. To obtain control data for water content of left lung right postcaval lobe was resected. Left hilum was snared with umbilical tape after collapse of left lung and tightened to clamp. It was maintained for 90 min. Thereafter, ventilation and perfusion of left lung were restored. To control group (n=6), prostacyclin was not given. To prostacyclin group (n=6), prostacyclin was intravenously administered at 250 ng/kg/min for 20 min, just before ischemia and just after reperfusion. We measured hemodynamic variables and analyzed arterial blood gas before and after ischemia and then at every 1 hour interval. At 4 hours after reperfusion, left lung was resected, and water content was measured with wet-dry method. RESULTS: There was no significant difference between control group and prostacyclin group in ABGA, PVR and water content of lung. However, three subjects of prostacyclin group showed higher PaO2 after reperfusion than that of others. CONCLUSION: This study shows that protective effect of prostacyclin is not uniform in severely injured canine ischemia-reperfusion model. We conclude that prostacyclin does not have pulmonary protective effect in severe ischemia-reperfusion injury.