Chemokines are a large family of secreted cytokines whose main function is to mediate leukocyte directional migration. Most cancers contain chemokines and express chemokine receptors as a consequence of the activity of deregulated transcription factors or tumor-suppressor genes. Indeed chemokines expression at the tumor site dictates leukocyte infiltration and angiogenesis, while chemokine receptors expression by tumor cells promotes their growth and matastatization. Chemokines also have several indirect effects on tumor growth and are a relevant element in the cancer-related infl ammation. In this chapter we will describe technical approaches available to study the role of chemokines in leukocyte infiltration and tumor metastatization in murine tumor models.