Neutrophils have been implicated as the cause of vascular injury that can lead to organ dysfunction and organ failure following a variety of initiating events. In particular, neutrophils have been shown to be necessary for vascular or tissue damage to occur in ischemia-reperfusion injuries of some organs and in the generalized ischemia-reperfusion injury resulting from hemorrhagic shock. Adherence of neurotrophils to endothelium or homotypic aggregation of neutrophils is thought to be necessary for injuries of this type to occur and these cell-cell interactions are mediated by adhesion molecules on both endothelial cells and leukocytes. In our completed studies, monoclonal antibodies that recognize functional epitopes of the leukocyte CD11/CD18 provided protection from ischemia-reperfusion injury. In addition, preliminary studies investigating leukocyte L-selectin and endothelial P-selectin appear to provide protection from ischemia-reperfusion injury.