Stromal cell-derived factor-1 (SDF-1), a member of the CXC chemokine family, is constitutively produced by bone marrow stromal cells, and it induces chemotaxis on a variety of cell types that contain the G-protein–linked receptor CXCR4. SDF-1 plays a key role in hematopoiesis, and its involvement in migration, homing, and survival of hematopoietic progenitors has been well established. It is the first chemoattractant agent reported for human CD34 progenitor cells (1), and it promotes CD34 cell survival by counteracting apoptosis (2). SDF-1 may also have a role in neoangiogenesis. It increases production of vascular endothelial growth factor (VEGF), the main angiogenic factor, which in turn enhances the expression of CXCR4 receptor in endothelial cells, in an autocrine loop (3). SDF-1 may participate in atherothrombosis. It is a potent chemoattractant of monocytes and lymphocytes