Background/Aims: Helicobacter pylori is present worldwide but few large population studies exist on the epidemiology of the infection in Saudi Arabia. This is an urban based study which was undertaken to determine the prevalence of H. pylori infection among outpatients suffering from gastrointestinal symptoms attending large hospital in Riyadh, Saudi Arabia. Methods: A validated enzyme-linked immunosorbent assay (ELISA) was used for this study with 5782 samples collected from the outpatients population suffering from gastrointestinal (dyspeptic) symptoms, aged 2 to 82 years. Results: H. pylori seroprevalence was 67% increasing with age. Female shows higher prevalence of H. pylori infection than male. H. pylori infection was more common in patients suffering from epigastric pain. Conclusions: The seroprevalence rate was higher in female than male. This study shows a high prevalence of H. pylori infection in a large series of patients in an urban area of Saudi Arabia. (Korean J Gastroenterol 2008;52:226-229)