We examined the immunophenotypic characteristics of natural killer (NK) cell subsets in patients with severe atopic dermatitis (AD), rhinitis allergica (RA) and in healthy controls. Expression of CD16, CD56 and CD57 antigens on peripheral blood lymphocytes was evaluated by simultaneous double immunocytofluorometry. Our results showed significantly lower percentages of cells with CD16, CD56 and CD57 surface antigens in patients with AD. Furthermore subdivision of the AD group into two subgroups, AD1 and AD0 (with and without antigen-specific IgE antibodies against potent inhalative allergens, i.e. mite, grass, rye, birch, cat) revealed that patients of subgroup AD1 showed a more prominent decrease compared to that of subgroup AD0. Moreover, we found a significant negative correlation between the percentage of CD56 + CD16 + NK cells and total IgE levels in serum, which were significantly higher in patients of subgroup AD1 than in AD0. NK cell activity was deficient in patients with AD but there was no difference between both subgroups. These data indicate that considerable heterogeneity in immunologic regulation may exist in patients with AD with regard to their NK cell subsets.