Given that (1) macrophages are required for tumor recruitment and localization to the pre-metastatic niche3, 5, 19, (2) immune cells are known to localize to lungs in a CXCR3-dependent manner10, 11, and (3) the production of CXCR3 ligands in the lung is induced by introduction of circulating melanoma cells11, we hypothesized that CXCR3+ monocytes/macrophages may facilitate tumor engraftment in lung. This evidence concerns the gene CXCR3 and melanoma.