From a group of 92 patients receiving grass pollen immunotherapy, and selected on grounds of high IgG4 titers against Lol p I, sera were tested for IgG4 antibodies against the glycosylated grass pollen allergen Lol p XI. In 72 of 92 cases IgG4 antibodies were demonstrated. The N-glycan of Lol p XI was earlier shown to be an epitope for IgE antibodies. In the present study it was demonstrated that the carbohydrate structure is also recognized by IgG4 antibodies, illustrating that IgG4 responses are not immuno-restricted to peptide epitopes, as was suggested in several reports.