Chemokines are a family of structurally related proteins that share the ability to induce migration of specific subsets of leucocytes. These specialised cytokines play a critical part in the generation of cellular inflammation, both in the protective responses to invading pathogens and in the pathological processes associated with infection and immune-mediated diseases. Chemokines are more than simple chemotactic factors, since they are also implicated in leucocyte activation, angiogenesis, and antimicrobial functions, including a protective role in HIV infection. These molecules provide potentially valuable targets for therapeutic intervention in a wide range of diseases.