Using isolated perfusion rat lung model, we studied the effect of continuous ventilation without perfusion and allopurinol on the development of ischaemia-reperfusion lung injury. Ischaemia was induced by stopping the perfusion. Normothermic ischaemia for 90 min without ventilation caused significant lung oedema. Continuous ventilation during ischaemia with 21% O2 decreased lung oedema significantly after 60 min of reperfusion. The same protection could be achieved by 100% N2 ventilation during 90 min of ischaemia, suggesting that xanthine oxidase (XO) is unlikely to cause the ischaemia-reperfusion lung injury. On the other hand allopurinol, XO inhibitor, equally inhibited lung oedema after 90 min of ischaemia and 60 min of reperfusion. These results indicate that mechanical movement of alveoli provides successful preservation of ischaemic lung, and allopurinol has some protective effect other than XO inhibition.