The Rome II criteria and questionnaires developed to identify functional gastrointestinal disorders have not been evaluated. Our objectives were to determine the prevalence of functional gastrointestinal disorders in Canada, compare our results with data from other published studies, assess concordance of Rome I and Rome II criteria for irritable bowel syndrome, and suggest improvements in the Rome II questionnaire. An independent research firm was employed to conduct a random digit dial national survey, inviting household members > or = 18 years of age to participate in a study examining personal health issues. Subjects recruited by telephone, who agreed to participate, were mailed a questionnaire, and the data were retrieved by a follow-up phone call. The Rome II questionnaire and algorithms were used and where possible Rome I algorithms were also applied. At least one functional gastrointestinal disorder occurred in 61.7% of 1149 respondents (65.6% female versus 57.6% male; P < 0.05). The most prevalent were the functional bowel disorders at 41.6% followed by esophageal disorders at 28.9%. Irritable bowel syndrome prevalence by Rome II and I criteria were 12.1% and 13.5%, respectively (kappa = 0.76). Because the Rome II criteria have added exclusion items that are not present in the Rome I criteria, the prevalence of esophageal, gastroduodenal, and anorectal disorders is lower than the figures from a US market survey. In conclusion, functional gastrointestinal disorders are highly prevalent in Canada, with a significantly higher rate in women. There is substantial agreement between Rome I and Rome II criteria for irritable bowel syndrome. Rome criteria and questionnaire remain works in progress.