I. Introduction Eosinophils accumulate in the site of the inflammatory focus in allergic-type responses associated with asthma and immune reactions against helminthic parasites (1 ). This accumulation is believed to be regulated by a complex series of events that involve T ceHs and cytokines (2,3). Cytokines were originally considered to be derived predominantly from lymphocytes and other monocytic ceUs. However, recent progress in cytokine research has shown that many other ceH types may also elaborate these proteins. Our previous understanding of the nature of blood and tissue eosinophils relied on the assumption that since they are predominantly "end cells," they are limited in their capacity to transcribe and translate new proteins. However, a number of laboratories during the last few years have examined the ability of the eosinophil to elaborate new proteins and have demonstrated that, like many other inflammatory ceHs, the eosiniphil is capable of synthesizing, storing, and releasing a considerable number of important inflammatory and regulatory cytokines, growth factors, and chemokines. The aims of this article are to review this area and to discuss the biological signifi-
cance of cytokine production by eosinophils within the context of immunoglobulin E-(lgE-) dependent allergic inflammation and eosinophilassociated disease conditions.