Expression of low‐affinity receptors for IgE (FcɛRII) on T and B cells was examined with monoclonal antibodies to cell surface antigens of FcɛRII (CD23), T cells (CD3) or B cells (CD 19) by two‐dimensional analysis under laser flow cytometry system. The majority of cells bearing FcɛRII were B cells; however, a small proportion of T cells (1. 6%) bore FcɛRII in children with atopic asthma and elevated serum level of IgE. The occurrence of FcɛRII positive B cells was also increased in children with atopic asthma compared with non‐atopic controls (p<0.001). The numbers of T and B cells hearing Fc receptors for IgG (FcɛR) did not differ between atopic and non‐atopic children. T cells were isolated from venous blood by rosetting with sheep erythrocytes, and then culturedin vitrowith phytohemagglutinin plus phorbol‐myristate‐acetate. The amount of IgE‐binding factors (IgE‐BF), a soluble form of FcɛRII, was determined by means of enzyme‐linked immunosorbent assay. The level of IgE‐BF was increased in cultures from children with a atopic asthma compared with non‐atopic controls (p<0.01). The possible involvements of FcɛRII on T cells and their soluble products, IgE‐BF, in the pathogenesi