An essential component of inflammation is the migration of circulating leukocytes from blood into tissues. This process is characterized by a multistep paradigm of sequential cell adhesion and activation events that lead to the extravasation of specific leukocyte subsets to different tissues in health and disease. The first step of leukocyte extravasation, the rolling of leukocytes, is primarily mediated by the interactions of selectins and their ligands. It has recently become evident that fucosyltransferases are crucial for selectin ligand synthesis, inflammation, and skin homing. This book provides an in-depth overview of the mechanisms of leukocyte trafficking and of the molecular mechanisms of selectin/selectin ligand interactions and discusses options for pharmacological intervention to treat inflammatory diseases.