Among the earliest signs of inflammation is the capture of leukocytes from the blood stream and their subsequent rolling along the endothelium of postcapillary venules. This commentary summarizes recent insight into the molecular basis of leukocyte rolling gained from gene-targeted mice, Ab blocking studies, and in vitro and in vivo reconstitution assays. These data reveal how the selectins individually and collectively contribute to the process of leukocyte capture and subsequent rolling on vascular endothelium.