CCR3, a receptor for chemokines such as eotaxin-1,-2,-3, MCP-2,-3,-4, and RANTES, is expressed on the surface of eosinophils, mast cells, basophils, and Th2 lymphocytes and, intracellularly, in mast cells. In addition, CCR3 is also found on dendritic cells, astrocytes, and microglial cells in the brain. CCR3 plays an important role in the pathology of acute and chronic inflammatory conditions such as allergic rhinitis, asthma, and airway hyperresponsiveness (AHR), and seasonal conjunctivitis. CCR3 mediates recruitment of eosinophils, basophils, and Th2 lymphocytes to the site of inflammation. CCR3 in and/or on mast cells also mediates trafficking of progenitors, selective programming of mast cell phenotype and effector function, and differentiation and selective development of mast cells to different subtypes. Therefore, CCR3 constitutes an attractive target for therapeutic intervention.