CXC chemokine receptor 3 (CXCR3), which is known to be expressed predominately on memory and activated T lymphocytes, is a receptor for both interferon γ (IFN-γ)–inducible protein 10 (γIP-10) and monokine induced by IFN-γ (Mig). We report the novel finding that CXCR3 is also expressed on CD34⁺ hematopoietic progenitors from human cord blood stimulated with granulocyte-macrophage colony-stimulating factor (GM-CSF) but not on freshly isolated CD34⁺ progenitors. Freshly isolated CD34⁺progenitors expressed low levels of CXCR3 messenger RNA, but this expression was highly up-regulated by GM-CSF, as indicated by a real-time quantitative reverse transcriptase–polymerase chain reaction technique. γIP-10 and Mig induced chemotaxis of GM-CSF–stimulated CD34⁺ progenitors by means of CXCR3, since an anti-CXCR3 monoclonal antibody (mAb) was found to block γIP-10–induced and Mig-induced CD34⁺ progenitor chemotaxis. These chemotactic attracted CD34⁺ progenitors are colony-forming units—granulocyte-macrophage. γIP-10 and Mig also induced GM-CSF–stimulated CD34⁺ progenitor adhesion and aggregation by means of CXCR3, a finding confirmed by the observation that anti-CXCR3 mAb blocked these functions of γIP-10 and Mig but not of chemokine stromal cell–derived factor 1α. γIP-10–induced and Mig-induced up-regulation of integrins (CD49a and CD49b) was found to play a crucial role in adhesion of GM-CSF–stimulated CD34⁺progenitors. Moreover, γIP-10 and Mig stimulated CXCR3 redistribution and cellular polarization in GM-CSF–stimulated CD34⁺progenitors. These results indicate that CXCR3–γIP-10 and CXCR3–Mig receptor-ligand pairs, as well as the effects of GM-CSF on them, may be especially important in the cytokine/chemokine environment for the physiologic and pathophysiologic events of differentiation of CD34⁺ hematopoietic progenitors into lymphoid and myeloid stem cells, subsequently immune and inflammatory cells. These processes include transmigration, relocation, differentiation, and maturation of CD34⁺ hematopoietic progenitors.