Pollen proteins, separated under dissociating conditions on polyacrylamide gels, were electrophoretically transferred to nitrocellulose and probed with sera from subjects allergic to grass pollens. By using a large enough panel of patients' sera, the complete spectrum of IgE-binding proteins in a pollen extract may be rapidly defined. When this procedure was applied to some of the best studied pollen species, all of the protein allergens previously described were found but, in every case, additional IgE-binding proteins were also detected. For example, although perennial ryegrass (Lolium perenne) has been investigated by other techniques since the 1960's, with the resultant identification of 6 allergens, a further 8 allergens were demonstrated in our electroblotting studies. The number of allergens identified in the other species examined ranged from 13 for Dactylis glomerata and 14 for Triticum aestivum to 19 for Poa pratensis. In addition to the capacity of protein blotting to identify a greater range of pollen allergens more quickly and precisely than any other technique used, the method may help to identify allergenic proteins that may be species-specific. © 1990.