T and B cells bearing Fc receptors for IgE (Fc epsilon R) were studied in 7 patients with hyperimmunoglobulinemia E (2 with hyper IgE syndrome and 5 with Kimura's disease). Fc epsilon R was detected by both rosette formation with IgE-coated red cells (Eo'-IgE) and immunofluorescence assay using H107 monoclonal antibody recognizing a determinant(s) associated with lymphocyte Fc epsilon R. A high correlation was observed between the proportions of Eo'-IgE rosette-forming cells (RFC) and H107+ cells. All patients had a large number of Fc epsilon R-positive cells (mean +/- 1 SD; 9.7 +/- 3.7% Eo'-IgE-RFC, 8.4 +/- 3.4% H107+ cells) in contrast to those of 6 normal subjects (0.7 +/- 1.2% Eo'-IgE-RFC, 0.3 +/- 0.4% H107+ cells). In one patient with Kimura's disease, the presence of Fc epsilon R-bearing T cells was confirmed by two-dimensional flow cytometry, using fluorescein isothiocyanate (FITC)-H107 and phycoerythrin (PE)-Leu-1. H107 antigens seemed to be expressed on both helper/inducer and suppressor T-cell populations. The direct analysis of Fc epsilon R+ T cells by 2-D flow cytometry with H107 antibody may facilitate the study of hyperimmunoglobulinemia E.