The exact pathomechanism of jejunal damage caused by gliadin in coeliac disease has not been clarified. 0.3 g of gluten per kg bodyweight was administered to 14 children affected by coeliac disease, being on gluten-free diet, five hours before jejunal biopsy. There was no change in the number of intraepithelial lymphocytes and eosinophils while cellular infiltration of the lamina propria exhibited a marked increase and the number of mast-cells per tissue unit significantly decreased as compared with controls. It is concluded that mast-cells may play an important role in the mechanism of gluten induced jejunal damage.