Recent studies have implicated soybeans as one of the major food allergens in children. Serum from eight patients with atopic dermatitis and positive double-blind, placebo-controlled food challenges to soy were used to investigate allergen-specific IgE and IgG antibody to soy protein and its fractions. ELISA and immunoblotting techniques were used for this purpose. A crude soy extract, as well as the 7S, 11S, and whey fractions, were isolated and purified for the in vitro studies from commercial defatted soy flakes. ELISA results demonstrated a statistically significant increased IgE and IgG response to the crude soy extract compared to that of normal control subjects. There was also an increase in IgE specific for 7S and IgG specific for 11S in the atopic group. The immunoblots reveal that IgE and IgG are present in varying amounts to multiple fractions of the soy protein. These results indicate that IgE and IgG specific to crude soy are elevated in patients with positive double-blind, placebo-controlled food challenges to soy but that no one fraction is clearly more antigenic.