Endothelial cells (ECs) do more than just play a role in distinguishing blood and tissues. These cells are also influenced by various chemical mediators present in the blood and tissues. In addition, they produce diverse cytokines, chemokines, adhesion molecules, and growth factors. Therefore, ECs are actively involved in the inflammatory and immune response. We investigated the effects of intravenous immunoglobulin (IVIG) and methylprednisolone (MP) on activated human ECs, by examining the individual and combined effects of the drugs. Human umbilical vein ECs (HUVECs) obtained from the umbilical cords of healthy newborns were cultured. After the HUVECs were treated with interleukin (IL)-1beta, the effects of IVIG and/or MP on the activated HUVECs were assessed by cell proliferation, mRNA expression, and the production of vascular cell adhesion molecule (VCAM)-1, IL-1beta, and vascular EC growth factor (VEGF). IVIG and MP inhibited HUVEC proliferation. IVIG and MP significantly down regulated mRNA expression and the production of VCAM-1, IL-1beta, and VEGF. The combination of IVIG and MP generally showed a greater suppressive effect on mRNA expression and on the production of VCAM-1, IL-1beta, and VEGF. Our results suggest that some of the corticosteroid-sparing effects of IVIG observed in patients with severe asthma could be related to a decreased ability of ECs to proliferate, and to a down regulation of the expression of molecules involved in the onset and progression of airway inflammation.