Peripheral blood lymphocytes from 22 patients with atopic dermatitis, 17 age-matched healthy controls, 10 patients with other skin diseases, and 14 patients with either asthma or allergic rhinitis were characterized by reactivity with monoclonal antibodies to the surface antigens of helper-inducer (T4) and suppressor-cytotoxic (T8) T cell subsets and to a common T cell antigen (T3). In contrast to healthy controls and controls with other skin diseases or respiratory allergic disease, patients with atopic dermatitis had a reduced percentage of T3-positive (T3+)cells (p less than 0.01) and T8-positive (T8+) cells (p less than 0.001) but not of T4-positive cells (T4+)op less than 0.05). A selective increase in the ratio of T4+ cells over T8+ cells was observed in 17 of 22 patients with atopic dermatitis but not in any of the controls. Thus there is a loss of circulating suppressor-cytoxic T cells in the majority of patients with active atopic dermatitis.