It has been shown that GGT activity in the duodenal biopsy homogenates of the children with coeliac disease (n-10) in remission (1 to 3 years of gluten-free diet) is lower than in those with other gastrointestinal tract diseases (n-6). In children with coeliac disease after gluten challenge (1 g of gluten) kg BW for 3 to 6 months) the GGT activity decreased fourfold (n-10). After a few months of gluten challenge there was in coeliac children (n-5) a marked predominance of GGT without sialic acid (the asialic GGT). Similarly there was a prevalence of this form (n-5) in the gut tissue of 3 month old human fetus. In the homogenates of the duodenal bioptates of the children with other gastrointestinal tract diseases (n-6) there was a predominance of the sialic form of the GGT. In the gut tissue of children older than 3 years (n-6) and adults who died of reasons other than gastrointestinal a marked predominance of the sialic form of GGT was found. It has been suggested that presence of asialic form of GGT in coeliac disease is connected with the lectin-like activity of gluten. The process of sialization or desialization takes place within or outside enterocytes. It changes the gut permeability and causes a secondary reaction to the penetrating allergens.