We have recently reported the creation of the first immortalized cell line derived from human dermal microvascular endothelial cells (HMEC-1). In preliminary studies this line was found to closely resemble microvascular endothelial cells in regard to many phenotypic characteristics. Because two key functional features of endothelial cells are their ability to bind to peripheral blood leukocytes and extracellular matrix proteins via cell adhesion molecules, we have now characterized HMEC-1 in terms of expression and regulation of cell adhesion molecules of the integrin, immunoglobulin gene superfamily, and selectin families. HMEC-1 can either constitutively express or can be induced to express key integrins, including alpha-1, -2, -3, -4, -5, -6, and -V, as well as beta-1, -3, -4, and -5. They also express or are capable of expressing immunoglobulin gene superfamily molecules, such as intercellular adhesion molecule-1 and vascular cell adhesion molecule-1, and a member of the selectin family, E-selectin. A number of important cell adhesion molecules that are either constitutively expressed or that must be induced are regulated in a time- and dose-dependent fashion by selected cytokines. Experiments comparing the phenotypic characteristics of HMEC-1 with human dermal microvascular endothelial cells or human umbilical vein endothelial cells reveal HMEC-1 to have features of both small- and large-vessel endothelial cells.