In order to determine the effect of ultraviolet radiation (UVR) on the cell adhesion molecules expressed in human dermal microvascular endothelial cells (HDMEC), the cells were exposed to varying UVR doses and the cell surface was examined for expression of intercellular cell adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM- 1), and E-selectin. The effect of UVB irradiation on the binding of T lymphocytes to HDMEC was also examined. UVA irradiation did not affect the surface expression of ICAM-1, VCAM-1, or E-selectin on the HDMEC. However, following UVB exposure, ELISA demonstrated a significant increase in the baseline ICAM-1 cell surface expression on the HDMEC. However, no induction of either E-selectin or VCAM-1 was noted. UVB also significantly augmented ICAM-1 induction by IL-1α and TNF-α. VCAM-1 was induced by stimulating HDMEC with IL-1α following a UVB irradiation dose of 100 mJ/cm². Flow cytometric analysis of the HDMEC stimulated with IL-1α for 24h demonstrated that 12% of the cells expressed VCAM-1 but either IL-1α or UVB irradiation alone failed to induce VCAM-1 expression. Enhancement of T cell-HDMEC binding by IL-1 α; or TNF-α treatment was not significantly affected after UVB irradiation. This study demonstrated that UVB irradiation can alter ICAM-1 and VCAM-1 expression on the HDMEC surface and that augmentation of ICAM-1 expression and the IL-1α-dependent induction of VCAM-1 following UVB exposure might be important steps in the pathogenesis of sunburn.