Discovery of new genes and proteins directly supporting leukocyte adhesion is waning, whereas there is heightened interest in the cell mechanics and receptor dynamics that lead from transient tethering via selectins to affinity shifts and adhesion strengthening through integrins. New optical tools enable real-time imaging of leukocyte rolling and arrest in parallel plate flow channels (PPFCs), and detection of single-molecule force spectroscopy provides an inner view of the intercellular adhesive contact region. Leukocyte recruitment during acute inflammation is triggered by ligation of G protein–coupled chemotactic receptors (GPCRs) and clustering of selectins. This, in turn, activates β₂-integrin (CD18), which facilitates cell capture and arrest in shear flow. This review provides a conceptual model for the molecular events supporting leukocyte recruitment.