Investigation of leukocyte sequestration in alveolar capillaries and of microhemodynamic changes after pulmonary ischemia/reperfusion injury. The kinetics of leukocyte passage and the hemodynamics in pulmonary microcirculation were investigated in 16 rabbits by intravital microscopy. Mean red blood cell velocity and the number of sticking leukocytes were measured in pulmonary arterioles, venules, and capillaries after 1 hour of tourniquet ischemia and 10 minutes and 1 hour after reperfusion. The decrease of red blood cell velocity after reperfusion was associated with a largely increased heterogeneity of blood flow. Immediately after the onset of blood flow, sequestered leukocytes were found in all microvascular segments. An increased number of leukocytes was present in arterioles, venules, and alveolar capillaries 10 minutes and 1 hour after reperfusion. Concomitantly, width of alveolar septa was increased while arterial oxygen tension was reduced, indicating the development of interstitial pulmonary edema. Leukocytes are sequestered after pulmonary ischemia and reperfusion not only in alveolar capillaries but also in arterioles and venules, and they may contribute to the development of reperfusion edema.