Sera from forty-six patients with dermatitis herpetiformis (DH) were examined for anti-gliadin antibodies (AGA) by the enzyme linked immunosorbent assay (ELISA) test and by a simple new immunofluorescent (IF) test. AGA were present in fifteen out of thirty-two patients taking a normal diet, but in none of the fourteen taking a gluten-free diet (GFD). The presence of circulating AGA was related to the severity of the enteropathy. AGA were present in all ten patients with a flat mucosa and in four of six with a convoluted mucosa, but in only one out of thirty patients with normal morphology of the small intestine. However, in those patients taking a normal diet and with a normal morphology of the intestine there was evidence of gluten sensitivity compared to those taking a GFD, as the intraepithelial lymphocyte count (IELC) was significantly raised in the peri-nuclear and supra-nuclear positions. The study shows that the presence of AGA in the serum is a good indication of the degree of gluten sensitivity as expressed by severe mucosal damage in patients with DH.