The binding of human IgE myeloma proteins to 16 human cultured lymphoblastoid cell lines was studied by measuring specific uptake of radiolabeled deaggregated IgE myeloma proteins and/or E-IgE rosette formation. Eight lines, RPMI-8866, Wil-2WT, RPMI-6410, RPMI-1788, RPMI-4265, Clowers, COLO-59 and Victor, bound IgE as shown by at least one of these methods. The lines, RPMI-4098, SCRF-5004, NC-37, Daudi, Raji, P3JHR-1, RPMI-1301 and Molt-4 did not bind IgE. Of the positive cell lines, 58 to 98% of the cells formed E-IgE rosetts. The binding of IgE was Fc fragment specific. It could only be inhibited by human IgE and its Fc fragment but not by IgE Fab fragments and Ig of other classes. The binding of IgE also appeared to be species specific, since a rat IgE myeloma protein did neither bind to the cells nor inhibit the binding of human IgE. The binding of IgE was relatively temperature independent and was abolished by trypsin and pronase pretreatment of the cells. Most of the cell lines binding IgE did not bind IgG but had surface immunoglobulin and did not form spontaneous E rosettes. These data suggest that certain lymphoblastoid cells may have receptors for IgE.