Résumé : Of 1,100 patients checked by at least two diagnosis tests (urease, histology, culture) 574 (52.1 p. 100) were found to have Campylobacter pylori (C. pylori) in their antral mucosa. Significantly frequencies of C. pylori (p < 0.005) were evidenced in the group of patients with active gastroduodenal ulcer (212/298, 71 p. 100), in non ulcer dyspepsia (NUD) with a previous history of GD ulcer (108/177, 61 p. 100) and NUD without antecedent history of GD ulcer (254/625, 41 p. 100). Whatever the group, males and immigrants were significantly at risk. Chronic alcoholism (>60 g/day) and non steroid antiinflammatory drugs (NSAID) intake were not predictive for the presence of C. pylori but smokers were significantly at risk when the total (n = 1,100) population was taken into consideration. C. pylori was found in 29 p. 100 of asymptomatic controls (n = 31). There was no significant difference in the frequency and intensity of symptoms when comparing C. pylori+ and C. pylori- patients. The macroscopic aspect of the antral mucosa was not predictive since 51 p. 100 patients with normal endoscopy were C. pylori+. A strong correlation was observed between the incidence of C. pylori and the severity of gastritis at histology (p < 0.001) and C. pylori was found in 7 p. 100 of patients with normal histology. A sympatomatic index was prospectively established for 200 out-patients with NUD: in 70 C. pylori+ patients, improvement of symptoms was observed whatever the treatment (bismuth salts, amoxicillin, anti-H2, placebo) but significant rates of C. pylori clearance and improvement of gastritis were observed only in patients treated with bismuth salts or amoxicillin.