Wheat proteins were fractionated into salt-soluble, glutenin-rich, and gliadin-rich fractions. Reactivities of these protein fractions with sera of patients with wheat-associated allergies were examined under various conditions. The relative reactivity of the fractions was generally in the order glutenin-rich > gliadin-rich >> salt-soluble fractions, although their reactivities were variable among patients and among the reaction conditions, indicating that the kind, the number and the epitope of allergens were variable among patients. To identify major allergens, alpha-, gamma- and omega-gliadin, and low-molecular-mass (LMM)- and high-molecular-mass (HMM)-glutenin genes were expressed in Escherichia coli by means of a pET vector. Recombinant gliadins and glutenins were partially purfied on the basis of the solubilities of prolamin and glutelin. The partially purified recombinant proteins were reacted with the patients' sera. LMM glutenin containing many Gln-Gln-Gln-Pro-Pro motifs, which was identified to be IgE-binding epitope [Tanabe, S., Arai, S., Yanagihara, Y., Mita, H., Takahashi, K. & Watanabe, M. (1996) Biochem. Biophys. Res. Commun. 219, 290-293], exhibited the highest reactivity. The next highest reactivities were observed on alpha-gliadin and gamma-gliadin, which had not been identified as allergens.