The aim of our study was to evaluate the relationship between Helicobacter pylori infection and various gastroduodenal diseases. We also took into consideration alcohol intake and smoking. Two-hundred and fifty-three consecutive patients with ulcer-like symptoms underwent gastroscopic and histological examinations. H. pylori status was evaluated by means of culture, Giemsa stain and CP-test, upon obtaining bioptic samples of gastric mucosa. Two hundred eighteen patients were affected by gastritis, 171 of which were H. pylori positive (78.4%); of 164 patients with active gastritis, 158 were H. pylori positive (96.3%). In 63 patients with duodenal ulcer, H. pylori was present in 58 cases (92.1%). Of 14 patients with gastric ulcer, 11 were H. pylori positive (78.6%). Out of 133 patients with duodenitis associated with active ulcer or a history of previous ulcer, H. pylori was found in 112 patients (84.2%). Among the 27 patients with "autonomous" duodenitis, 18 were H. pylori positive (66.6%); the comparison between the two groups of patients with duodenitis concerning H. pylori infection was statistically significant (p = 0.033). Of the 119 patients tested for acquired MALT, 39 were found positive (32.7%); among these 34 patients were H. pylori positive (87.1%) and only 5 patients were H. pylori negative (12.9%). Thus our study confirms the importance of H. pylori in gastroduodenal pathology underlining its role in the development of acquired MALT (mucosa associated lymphoid tissue) for its possible evolution in low grade B cell primary gastric lymphoma. Alcohol intake and smoking do not appear to play a role in H. pylori infection.