The purpose of the present study was to determine whether wheat alpha-amylase inhibitor subunits bind IgE sera from Japanese with atopic dermatitis (AD) related to wheat. IgE in sera from eight out of the 11 patients with RAST value of 3 or 4 against wheat-bound salt-soluble proteins of wheat and the alpha-amylase inhibitor proteins separated by gel filtration chromatography. The subunits of tetrameric alpha-amylase inhibitor, CM2, CM3 and CM16 (molecular weight approximately 14 kd), known to be major allergens for baker's asthma, were purified. Then the binding activity to IgE sera from the AD patients was examined by immunoblotting. The IgE sera bound only to CM3, not to CM2 and CM16. These results suggest that CM3 may be involved in both atopic dermatitis and baker's asthma.