The relationship between adenovirus type 12 (Ad12), celiac disease (CD) and dermatitis herpetiformis (DH) was evaluated by enzyme-linked immunosorbent assay (ELISA). Diagnostic phase serum samples from 44 children with CD, 16 children with DH and 60 matched controls were studied for serum antibodies to synthetic peptides derived from an early E1b protein of Ad12 and A gliadin. Both the patient groups had significantly (p < 0.01) higher IgG antibody levels to the Ad12 E1b peptide than the controls. The difference was especially pronounced for girls (p < 0.005). Antipeptide IgG antibodies to Ad12 E1b and A gliadin posed a synergistic increase in the CD and DH risk suggesting that infection with Ad12 is associated with CD and DH.