Biosynthetically-labeled carbohydrate-deficient rat IgE myeloma protein was obtained from IgE-producing IR 162 cells cultured in the presence of tunicamycin. Carbohydrate-deficient IgE molecules were purified by sequential use of fractional ammonium sulfate precipitation, affinity chromatography, and gel filtration. Lectin-Sepharose immunoadsorbents were used to separate carbohydrate-deficient IgE into a non-glycosylated IgE fraction and a partially-glycosylated IgE fraction. Both non-glycosylated and partially-glycosylated IgE were eluted later than native IgE upon gel filtration, and their epsilon chains each demonstrated faster mobility in SDS-polyacrylamide gel electrophoresis than the native epsilon chain. Both non-glycosylated and partially-glycosylaled IgE possessed the ability to specifically bind to IgE receptorbearing RBL-1 cells. Additional macromolecules comprised of one non-glycosylated epsilon-Iike chain with or without one disulfide-linked light chain were isolated from IgE-producing cells cultured with tunicamycin but did not bind to IgE receptors.