Immunoblots were used to compare the IgE-binding proteins of various soybean products using sera from 7 soybean-allergic patients. Blotting results indicate at least two distinct individualistic patterns of IgE binding to soy proteins. Serum IgE from individuals allergic to both peanuts and soybeans binds to several proteins with molecular weights ranging from 50,000 to 60,000 daltons, while IgE from individuals allergic to soybeans, but not peanuts, binds strongly to a protein(s) with a molecular weight of 20,000 daltons. The soy products tested displayed varying amounts of IgE binding with sera from sensitive patients.