The authors have studied the immunoglobulin heavy chain allotypes in 14 Sicilian patients with celiac disease (CD) and in 75 healthy controls. No association has been found between CD and Gm or Km phenotypes. When the role of Gm phenotypes in immune response against gliadin was analyzed, fb-positive CD patients on gluten-free diet for 1 year showed an increased antigliadin IgG response. Comparing the values of fb-positive subjects with those of negative ones, a significant difference was observed. These data, demonstrating that the presence or absence of a phenotype is able to define the breadth of immune response against alpha-gliadin antigen, are indicative of the role played by Ig allotypes in CD.