Tissue sections from the skin of patients with atopic dermatitis were investigated by means of hematoxylin-eosin staining, the avidin-biotin-peroxidase complex method, and double-labeling immunofluorescence using monoclonal antibodies to cell-surface antigens, including CD45R and CD29. In skin lesions of patients with atopic dermatitis, the epidermis was spongiotic and hyperplastic with little cellular infiltrate. Perivascular dermal infiltrate was significant and consisted primarily of mononuclear cells. The majority of the infiltrating mononuclear cells in the skin of patients with atopic dermatitis were CD4+ cells. Langerhans' cells were also increased in number. Furthermore, we investigated the subsets in the infiltrating CD4+ cells by double-labeling immunofluorescence using CD45R and CD29 monoclonal antibodies. Among the infiltrating CD4+ cells, CD4+CD29+ cells were dominant and CD4+CD45R+ cells were also present.