A complex mixture of pine (Pinus radiata D. Don) pollen proteins are rapidly released into aqueous solutions. IgE-binding proteins have been identified in these extracts using combined SDS-PAGE immunoblotting techniques. These IgE-binding proteins were detected using atopic patient and commerical pooled human sera known to be high in ryegrass-specific IgE. Enzyme-immunoassay inhibition studies revealed that leached P. radiata pollen proteins could partially inhibit serum IgE binding to ryegrass RAST discs thus providing preliminary evidence for allergen cross-reactivity between these two unrelated species.