CXC Chemokines play a important role in the process of leukocyte recruitment and activation at sites of inflammation. However, recent evidence suggests that these molecules can also regulate endothelial cell functions such as migration, angiogenesis and proliferation. In this study we have investigated CXC chemokine receptor expression in both primary cultures of human umbilical vein endothelial cells (HUVEC) and the spontaneously transformed HUVEC cell line, ECV304. We found that both cell types express mRNA for chemokine receptors CXCR1, CXCR2 and CXCR4, but not CXCR3. Flow cytometric analysis revealed low levels of CXCR1 but higher levels of CXCR4 cell surface expression. HUVECs responded to SDF-1α with a rapid and robust calcium flux, however no calcium flux was seen with either IL-8 or Gro-α. HUVECs and ECV304 cells did not proliferate in response to CXC chemokines, although ECV304 cells did migrate towards SDF-1α and IL-8. These data demonstrate that HUVECs and the endothelial cell line, ECV304 express functional CXC chemokine receptors.