Immune responses require the orchestrated migration of T cells throughout the body. Conventional CD4+ and CD8+ αβ T cells undergo clonal expansion in the secondary lymphoid tissues, during which they are programmed to migrate into specific non-lymphoid tissues and other lymphoid effector sites such as B cell follicles. By contrast, T cell populations expressing receptors with limited diversity (i.e. γδ T cells and NK T cells) appear to be preprogrammed to localize in non-lymphoid tissues where they monitor tissue integrity or serve regulatory functions. By promoting chemotaxis and integrin activation, chemokines and their receptors (in conjunction with surface adhesion molecules) control these T cell homing events. Thus, expression of chemokine receptors defines T cells with tropism for particular tissues and/or microenvironments, and identifies T cell subsets with distinct functional properties.