Thymus-expressed chemokine (TECK) has been reported to chemoattract dendritic cells, thymocytes, and activated macrophages. Here, we show that TECK is a specific agonist for a human orphan receptor called GPR-9-6. We have determined the cDNA sequence of human GPR-9-6 and cloned the corresponding murine cDNA. Human and murine GPR-9-6 expression is very high in the thymus and low in lymph nodes and spleen. RT-PCR analysis of murine GPR-9-6 expression on murine FACS-sorted thymocyte subpopulations showed that this gene is expressed in both immature and mature T cells. Additions of human or murine TECK to HEK 293/human GPR-9-6 and HEK 293/murine GPR-9-6 transfectants provoked intracytoplasmic calcium mobilization. Human TECK also induced the in vitro migration of HEK 293/human GPR-9-6 cells. These results confirm that GPR-9-6 is a specific receptor for TECK. According to the established nomenclature system, we propose to rename GPR-9-6 as CC chemokine receptor 9 (CCR9).