A high percentage of birch pollen allergic patients also experience food hypersensitivity which results from common epitopes on the corresponding allergens. In order to analyze whether this observed cross-reactivity can be attributed to common structural features, the major birch pollen allergen Bet v 1 and the cherry allergen Pru a 1 were investigated by multidimensional heteronuclear nuclear magnetic resonance (NMR) spectroscopy. For the 17 kDa Bet v 1 a three-dimensional structure was calculated on the basis of 1344 experimental restraints. The structure is well defined showing average root mean square deviations of 0.67 and 1.15 Å for the backbone heavy atoms and all heavy atoms of residues 1–154, respectively. The major structural features include a seven-stranded antiparallel β-sheet that wraps around a long C-terminal α-helix, thereby forming a large cavity in the interior of the protein. This structure served as template for the generation of an NMR-based model of Pru a 1 by homology modelling in conjunction with 277 experimentally derived distance restraints. Comparison to the structure of Bet v 1 proves both structures to be highly similar concerning the elements of secondary structure as well as the shape and charge distribution of the protein surface. This finding is consistent with the observed cross-reactivity between both proteins and allows the delineation of common cross-reactive B-cell epitopes.