Leukocytes migrate from the blood to sites of inflammation in response to locally produced chemoattractants that activate specific cell surface receptors. The primary structures of leukocyte receptors for N-formyl peptides, C5a, platelet-activating factor, and 8 of the 18 known human chemokines (interleukin-8 and related molecules) have been deduced from cloned cDNAs. All of these are seven-transmembrane-domain rhodopsin ญ like G protein-coupled receptors. Biochemical and molecular genetic analysis of the chemoattractant receptors indicates that the chemo ญ attractants may have both broadly overlapping as well as specialized roles in the regulation of acute and chronic inflammation. Interestingly, the chemokine receptors have functional homologues in human cytomegalo ญ virus and Herpesvirus saimiri. Moreover, the Duffy antigen, which mediates invasion of erythrocytes by Plasmodium vivax, a major cause of malaria, is also a chemokine binding protein. These surprising develop ญ ments suggest that in addition to leukocyte-mediated inflammation, the chemokines may also be involved in erythrocyte function and, through molecular mimicry, in microbial pathogenesis.