Type A chronic atrophic gastritis (CAG) is increased in type 1 diabetic patients (DM1). To address this issue, we determined and analyzed the number of peripheral blood regulatory T cells (Tregs) in 15 DM1-CAG patients, 15 DM1 patients without associated autoantibodies (DM1) and 15 healthy controls by flow cytometry and compared gastric Tregs expression (CD4+Foxp3+/CD4+) in DM1-CAG patients with that observed in 10 control Helicobacter pylori CAG-infected biopsies. The percentage of peripheral Tregs was higher in DM1-CAG patients compared to DM1 and controls (CD4+Foxp3+: 7.67 +/- 1.91% vs. 5.38 +/- 1.57% and 5.65 +/- 1.76%, P < 0.001, respectively), with no differences between DM1 and controls. Gastric mucosal Tregs were higher in H. pylori CAG than in DM1-CAG patients (31.31 +/- 5.52% vs. 7.68 +/- 3.70%; P < 0.001). Data suggest that Tregs are stimulated in patients with more than one autoimmune disease (DM1 + CAG) in an ineffectual attempt to control autoimmune response and that the number of Tregs in gastric mucosa implicated in the chronification of gastritis differs according to the etiology.