Objective: It has been suggested that the oral cavity and dental plaque might be a reservoir for Helicobacter pylori (Hp). In this study, our aims were to detect the prevalence of Hp colonization in dental plaque and tongue scrapings of patients with chronic gastritis and to investigate the effect of systemic treatment upon this colonization and eradication of Hp from gastric mucosa. Method and materials: Eighty-one patients (49 men, 32 women) were included in the study. Dental plaque and tongue scraping specimens were obtained and assessed with Campylobacter-like organism (CLO) test, prior to endoscopic examination. By endoscopy, 2 antral and 1 corpus biopsy samples were taken for histologic examination, and 1 antral biopsy sample was taken for CLO test examination. Results: Chronic gastritis was diagnosed in 63 (77.7%) of 81 patients. Dental plaque samples of 64 (79%) patients and tongue scraping samples of 48 (59.2%) patients were urease positive. Of the 63 patients with chronic gastritis, dental plaque and tongue scrapings were urease positive in 52 (83%) and 37 (59%) patients, respectively. After 14 days of triple drug therapy (omeprazole, clarithromycin, and amoxicillin), Hp was eradicated from the gastric mucosa of almost all of the patients, whereas no changes were detected in dental plaque and tongue scrapings by CLO test examination. Conclusion: Helicobacter pylori colonization, which seemed to be high in dental plaque and on the tongue, might play an important role in the pathogenesis of the reinfection process. In order to eradicate Hp from both the oral cavity and the gastric mucosa, studies should be performed to assess the effects of plaque control procedures in addition to present treatment modalities.