The histological appearance of reperfusion injury is pulmonary edema associated with leukocyte aggregation in the vessels. We hypothesized that leukocytes play an important role in reperfusion injury and that leukocyte depletion could prevent it. Eighteen white male rabbits were divided into 3 groups. After extirpation, the lungs in group 1 were not preserved, and were reperfused with whole blood that was taken from other white rabbits. In groups 2 and 3, after flushing with 100 ml of modified Collins' solution, the lungs were preserved in the same solution for 6 hours at 4°C. Lungs in group 2 were then reperfused with whole blood while lungs in group 3 were reperfused with leukocyte-depleted blood. We measured the water content of the lung to determine the degree of pulmonary damage, the malondialdehyde (MDA) levels in reperfused blood and lung tissue, the complement activity, and examined the histological findings. Group 2 showed severe pulmonary edema histologically, and a significantly higher water content and MDA level than the other groups. There was no significant difference in complement activity between the 3 groups. Leukocyte depletion was effective in reducing reperfusion injury of the lung.