The underlying mechanism of atopic dermatitis (AD) exacerbated by Staphylococcus aureus has not been established. However, we demonstrated recently that the majority of S. aureus strains colonized in the skin of Korean AD patients carried genes encoding staphylococcal enterotoxin A (SEA) and/or toxic shock syndrome toxin-1 (TSST-1). Objective: To clarify the role of staphylococcal superantigen, SEA in AD. Methods: With the lesional skin of 9 AD patients and normal looking skin of one healthy adult, we examined first the expression of SEA, staphylococcal enterotoxin B (SEB), and TSST-1 using immunohistochemical analysis. In addition, we investigated the effects of SEA on the expression of inflammation-related adhesion molecules and cytokines in human HaCaT keratinocytes and Human Umbilical Vein Endothelial Cells (HUVECs) by reverse transcriptase-polymerase chain reaction (RT-PCR) analysis and enzyme-linked immunosorbent assay. Results: Staphylococcal protein A (SPA) and SEA were detected with increased immunoreactivity in AD patients. However, TSST-1 showed mild-to-moderate immunoreactivity in AD patients, whereas SEB was minimally detected. In the double immunofluorescence investigation, SEA and SPA were well co-localized. SEA induced upregulation of adhesion moleculesand elicited inflammatory responses in HaCaT keratinocytes and HUVECs. Conclusion: This study demonstrates the importance of SEA as an immunoinflammatory triggering factor of AD in Koreans.