Vascular cell adhesion molecule-1 (VCAM-1) is an endothelial cell membrane glycoprotein that has been implicated in leukocyte/endothelial cell interactions in inflammation. In this study, we report the expression of VCAM-1 in primary cultures of human brain microvessel endothelial cells (HBMEC) under standard conditions and following bacterial lipopolysaccharide (LPS), tumor necrosis factor-alpha (TNF-alpha), interleukin-1 beta (IL-1 beta), or interferon-gamma (IFN-gamma) treatment. Surface expression was detected and quantitated by light and immunogold electron microscopy and ELISA. Unstimulated cerebral endothelial cells (EC) constitutively expressed low levels of VCAM-1. LPS, TNF-alpha, or IL-1 beta increased the overall intensity of surface staining and the percentage of cells expressing VCAM-1 in a time- and concentration-dependent manner. LPS had the most potent effect, followed by TNF-alpha and then IL-1 beta. IFN-gamma did not upregulate VCAM-1. The level of VCAM-1 expression increased by 12-24 hr and returned to unstimulated levels by 48 hr. Immunoelectron microscopy demonstrated that VCAM-1 was preferentially localized on the apical as compared to the basal surface in both unstimulated and cytokine-treated cells. In addition, the intensity of immunostaining was significantly greater in stimulated versus unstimulated EC. The polarization and significant upregulation of VCAM-1 after cytokine treatment suggest a possible role of this adhesion molecule in inflammatory and autoimmune processes within the central nervous system.