This study was undertaken to elucidate any quantitative abnormalities of T cells and T subsets(helper/inducer T cell: T cell and suppressor/cytotoxic. T cell; Tsc cell) in the peripheral blood and cutaneous lesion in patients with atopic dermatitis by using monoclonal antibodies, and to ascertain whether there are any relations bctwcen such immunologic abnormalities and the severity of the disease. Thirty seven patints(19 male, 18 female) were entered in this study, who vistited the Departement of Dermatology of Seoul National University Hospital frnrn February 1985 to November 1985. The control group comprised fifteen hea1thy children (8 male, 7 female). The peripheral blood samples of 30 patients and the skin biopsy specirnens of 29 patients were examinecl. Both were examined in 22 patients. The results showed that there was a quantitative abnormality in pcripheral blood Tsc cells in patients with atopic dermatitis and it could be related to the severity of the disease. The predominance of T cells seemed to be relatecl to the pathogenesis of atopic dematitis.