Chemokines are small, chemotactic cytokines that direct migration of leukocytes, activate inflammatory responses and participate in many other pleiotropic functions, including regulation of tumour growth. Chemokines modulate tumour behaviour by three important mechanisms: regulation of tumour-associated angiogenesis, activation of a host tumour-specific immunological response, and direct stimulation of tumour cell proliferation in an autocrine fashion. All of these mechanisms are promising points of cancer intervention, and preclinical mouse models suggest that chemokine antagonists and agonists could become important in the development of new anticancer therapies.