Recent studies have demonstrated that patients allergic to tree pollens and latex are often allergic to fruits and vegetables. Such crossreactivities may have derived from proteins which share common epitops. We have studied a number of major allergens in apple and latex and their crossreactivities to proteins from birch pollens, fruits and vegetables. One of the major allergens in apple, an 18 Kd protein, shares extensive sequence homology to a major allergen in birch pollen and also to a pathogenesis related protein in many plants. The Nterminal amino acid sequence of allergens in eggplant and cabbage were determined and shown to be identical to the N-terminal sequence of pathogenesis related proteins which are known to be potent allergens. Latex allergens also show crossreactivities to proteins in avocado, kiwifruit and banana. The B-cell epitops will be further characterized by using synthetic overlapping peptide sequences.