Dendritic cell migration to secondary lymphoid tissues is critical for Ag presentation to T cells necessary to elicit an immune response. Despite the importance of dendritic cell trafficking in immunity, at present little is understood about the mechanisms that underlie this phenomenon. Using a novel transwell chemotaxis assay system, we demonstrate that the CC chemokine receptor-7 (CCR7) ligands 6Ckine and macrophage inflammatory protein (MIP)-3β are selective chemoattractants for MHC class II high B7-2 high bone marrow-derived dendritic cells at a potency 1000-fold higher than their known activity on naive T cells. Furthermore, these chemokines stimulate the chemotaxis of freshly isolated lymph node dendritic cells, as well as the egress of skin dendritic cells ex vivo. Because these chemokines are expressed in lymphoid organs and 6Ckine has been localized to high endothelial venules and lymphatic endothelium, we propose that they may play an important role in the homing of dendritic cells to lymphoid tissues.