Cell-cell and cell-matrix interactions play vital roles in morphogenesis, inflammation, thrombosis, wound healing, immune surveillance, and growth and metastasis. A number of cell surface receptors, so-called cell adhesion molecules (CAMs), mediate these events in various cell types. In leukocytes and platelets, several CAM families interact with each other or with the extracellular matrix in a well-orchestrated manner, to bring these circulating cells to areas of antigenic challenge and tissue injury. Significant progress has been made recently in understanding the molecular basis of leukocyte recruitment into tissues and the formation of the hemostatic plug. Several murine or humanized monoclonal antibodies directed against key adhesion receptors that mediate these events have been found effective in taming immune and thrombotic injury in experimental animal models and in phase I clinical trials. These advances herald the arrival of a novel class of antiinflammatory and antithrombotic drugs, the antiadhesions, which will likely be effective in many clinical situations facing the nephrologist and internist.