Aim of this experience has been to evaluate the behavior of the chief cell mass, of the parietal cell mass and of the serum pepsinogen I in patients operated on for duodenal ulcer by the Billroth II compared to patients with chronic fundic gastritis in non operated stomach and to healthy controls. From the results, even in operated patients, emerges a progressive reduction of the two cell masses, in relation to the different degree of chronic gastritis of the stump, in analogy with chronic fundic gastritis in non-operated stomach. In chronic superficial gastritis no differences emerge between operated patients and patients with chronic superficial fundic gastritis in non operated stomach, while with the getting on the inflammation, it can be observed a higher fall of the parietal cell mass in operated subjects than in non operated ones. Such differences are even greater in relation with the evaluation of the time elapsed between the operation and the evaluation of the two cell masses. Furthermore, no significant differences have emerged between the two groups of patients as for serum pepsinogen I. Such data is not discriminant between the two conditions.