Functional GI disorders (FGIDs) are common in clinical practice, but little is known about the epidemiology of these disorders in the general population. We aimed to determine the prevalence, association with psychological morbidity, and health care seeking behavior of FGIDs in the population. A random sample of subjects (n = 4500) aged > or = 18 yr and representative of the Australian population were mailed a validated questionnaire. For these subjects we measured all Rome I GI symptoms and physician visits over the past 12 months, as well as neuroticism, anxiety, depression, and somatic distress. The response rate for the study was 72%. The prevalence of any FGID was 34.6%, and 62.1% of these subjects had consulted a physician. There was considerable overlap of the FGIDs (19.2% had more than two disorders). Independent predictors for an FGID diagnosis were neuroticism, somatic distress, anxiety, bowel habit disturbance, abdominal pain frequency, and increasing age. However, psychological morbidity did not independently discriminate between consulters and nonconsulters with an FGID. More than one third of the general population have one or more FGIDs. There seems to be a modest link between psychological morbidity and FGIDs, although other unknown factors seem to be more important in explaining health care seeking for these disorders.