Although IgA is present in the skin of patients with dermatitis herpetiformis (DH), the relationship of that IgA to the mucosal immune response is not known. The purpose of this study was to determine if IgA antibodies directed against tissue antigens, which are present in the serum of patients with DH, are also present in the gut secretions of these patients. Serum and gut secretions from 8 patients with DH and 5 control subjects were analyzed by indirect immunofluorescence for the presence of IgA antireticulin and antiendomysium antibodies. IgA antibodies against reticulin (3 of 8 patients) and endomysium (4 of 8 patients) were found in the serum of patients with DH. IgA antibodies were also present in the gut secretions of all of these patients, but not in subjects (patients with DH and controls) that did not have serum IgA antireticulin or antiendomysium antibodies. The presence of IgA antireticulin and antiendomysium in both the serum and gut secretions of DH patients suggests that these antibodies arise as a result of the mucosal immune response and that IgA of mucosal origin can persist in the serum of patients with DH.