Enzyme immunoassays for the quantitation of IgA1 and IgA2 antibodies to dietary antigens were developed. Serum IgA1 antibodies to bovine serum albumin (BSA) were detectable in 2/30 healthy adults, in 3/26 healthy children, and at high levels in 8/11 children with coeliac disease, without relation to gluten exposure. IgA1 antibodies to ovalbumin (OA) and beta-lactoglobulin (BLG) at high titers were seen in one coeliac child but were otherwise low or absent. IgA2 antibodies to BSA were detectable in 28/48 healthy subjects and in 8/11 coeliac children. IgA2 antibodies to OA and BLG were measurable in a few samples from each group. IgA1 antibodies to the gluten component glycgli were found at low levels in 15/56 normal sera, and anti-glycgli antibodies of the IgA2 subclass in 14/48 sera from healthy persons, also at low levels. IgA1 anti-glycgli antibodies were measurable in 5/11 sera from CD patients on a gluten-free diet. Elevated levels of IgA1 anti-glycgli antibodies were detected in all sera from CD patients challenged with gluten, except in 1 patient with a markedly reduced serum IgA level. In contrast, the IgA2 anti-glycgli antibody levels were unaffected. Thus, increased levels of IgA antibodies to dietary protein antigens in childhood coeliac disease were observed only within the IgA1 isotype.