Considerable progress has been made in our understanding of the molecular mechanisms involved in eosinophil and basophil migration into sites of allergic inflammation. It is clearly a staged process, each stage offering a level of control over the cell specificity and degree of migration. On the basis of current evidence, the various receptors and mediators involved are summarized in Table 4. Once in the tissues, eosinophils may persist for several days or weeks, surviving under the influence of locally generated cytokines, and this persistence may also partly explain the selective tissue accumulation of eosinophils and basophils. Understanding the molecular mechanisms involved in leukocyte migration may lead to the discovery of selective and effective antagonists to treat allergic disease by preventing cell migration. Results in a number of animal models already suggest that this approach may be successful. The development of drugs that can be tested in the clinic is awaited with much interest.