Human dermal microvascular endothelial cells are used to analyze the functions of microvascular endothelium in vitro. However, the low yield and short lifespan of these cells in culture has limited the types of analysis that could be performed. Human microvascular endothelial cells are typically grown in media containing supplements such as dibutyryl cyclic AMP, hydrocortisone, bovine brain extract, and antifungal agents, each of which increase the complexity of experimental design and interpretation of results. In the present study, endothelial cells were transferred after Ulex europeus-I selection into a simplified medium consisting of Endothelial Basal Medium 131, 10% fetal bovine serum, and 2 ng/ml basic fibroblast growth factor and analyzed over 3 mo. The human microvascular endothelial cells expressed the endothelial markers von Willebrand factor, CD31, P-selectin, and E-selectin. In addition, the cells showed increased proliferation in the presence of basic fibroblast growth factor (0.5 ng/ml) or vascular endothelial cell growth factor (10 ng/ml). Tumor necrosis factor-alpha-induced expression of E-selectin was similar in cells at Passages 3, 6, and 12, indicating that the cells maintained responsiveness to cytokines over several weeks. Furthermore, the endothelial cells attained a typical cobblestone morphology with increased cellular density and also formed capillarylike tubes on Matrigel. In summary, the human dermal microvascular endothelial cells display the expected endothelial characteristics when grown for several passages and, therefore, provide a valuable in vitro model for human microvascular endothelium.