T cells are critical mediators of inflammation and as such, their migration to inflammatory sites is a tightly controlled process involving a complex series of molecules expressed by a variety of cell types. As our appreciation of the mechanisms governing T cell surveillance, activation, differentiation, and subsequent homing to sites of inflammation has advanced, the opportunity to develop novel therapeutic agents that modulate the immune system has increased. Importantly, the possibility of specifically targetting subpopulations of effector cells raises the exciting potential for the development of novel agents that selectively modify the immune response to allergens, without resulting in generalized immune suppression.