Over the last decades important risk factors for gastrointestinal symptoms have shifted, which may have changed its population prevalence. The aim of this study was to evaluate the current predominance of gastrointestinal symptoms, evaluate related factors and assess health-related quality of life in the general population. A systematic review was undertaken of all studies published as of December 1997, on the population prevalence of upper gastrointestinal (GI) symptoms. Studies and papers excluded from consideration were those done on subjects attending hospital or primary care clinics, or who were hospitalized or institutionalized; or where studies were conducted in the workplace or on occupational groups. Studies meeting the following criteria were included in the comparative analysis: period studied, sample size and response rate all reported; vague terms such as 'dyspepsia' or 'indigestion' defined if enquired about; abdominal pain or discomfort enquired about; patients with a history, or evidence, of organic disease not excluded from the results. Follow-up studies on groups of patients previously studied were also not included. In the 10 selected studies, the reported prevalence of upper abdominal symptoms (mostly upper abdominal pain or discomfort) ranged from around 8% to 54%, while the prevalence of heartburn and/or regurgitation ranged from 10% to 48% for heartburn, from 9% to 45% for regurgitation and 21% to 59% for both/either. In the case of upper abdominal symptoms, the most likely explanation for the broad range of prevalence reported is variation in the definition of symptoms. In the case of heartburn and regurgitation, different understandings of these terms by different investigators and subjects may have contributed to the range of results. Symptom definitions and what is understood by them should be among the most important considerations when undertaking population prevalence studies on upper GI symptoms, to allow comparisons to be generated between studies.