Objective. To examine the in vitro expression of E-selectin, P-selectin, intercellular adhesion molecule 1 (ICAM-I), ICAM-2, vascular cell adhesion molecule 1 (VCAM-l), and platelet-endothelial cell adhesion molecule 1 (PECAM-1) by synovial microvascular endothelial cells (SMEC) in comparison with microvascular neonatal foreskin endothelial cells (FSE) and macrovascular human umbilical vein endothelial cells (HUVE).Methods. Cultured endothelial cells were treated for 4 hours with medium alone or tumor necrosis factor a (TNFa). The expression of endothelial adhesion molecules was evaluated by flow cytometry, cell enzymelinked immunosorbent assay, and Northern blot anaResults. SMEC continuously expressed E-selectin under basal culture conditions, whereas FSE and HUVE did not. TNFa treatment of rheumatoid arthritis (RA) SMEC resulted in sustained peak expression of Eselectin for up to 24 hours, which subsequently declined but remained elevated even at 72 hours. In contrast, peak E-selectin expression in FSE and HUVE occurred between 4 hours and 16 hours after TNFa treatment and then declined to near basal levels by 24-48 hours. SMEC expressed significantly higher levels of ICAM-1 compared with HUVE under basal culture conditions.