Atopic dermatitis is a chronic, relapsing inflammatory skin disorder characterized by local infiltration of T cells. To date, numerous reports have shown that Staphylococcus aureus may exacerbate atopic dermatitis, and superantigens produced by this organism are thought to be one of the major causative factors in atopic dermatitis. The purpose of this study was to evaluate the role of staphylococcal superantigen in atopic dermatitis by observing expression of the variable region of beta chain of T cell receptor (TCR V beta) in the inflammatory cells infiltrating cutaneous lesions of atopic dermatitis. Fourteen patients with atopic dermatitis were enrolled. Punch biopsy specimens were obtained from lesional and normal-appearing skin of all patients. The expression of TCR V beta was studied by means of immunohistochemical technique using monoclonal antibodies. In 4 out of 14 patients, the tendencies of preferential expression of specific TCR V beta were found in lesional skin. This study suggested that staphylococcal superantigen and its corresponding T cell subsets may act as causative or pathogenic factors in a subgroup of atopic dermatitis.