Leukocyte migration towards injury sites is directed by the interaction of chemokines with their receptors. The stages of migration are closely regulated events that involve chemokine-induced leukocyte adhesion, diapedesis and homing. Current research suggests a pathophysiological role for chemokines in diverse inflammatory states arising from viral, bacterial and parasitic infection, allergic and asthmatic reactions, atherosclerosis and arthritis. A role for chemokines in tumor immunity and angiogenesis has recently been demonstrated. A basis for the rational design of chemokine antagonists is emerging from a knowledge of tertiary structures and mutational analysis of chemokine ligands and receptors. Here, we discuss advances in knowledge about chemokine structure and function, with emphasis on potential therapeutic agents.