Functional gastrointestinal disease is believed to be very common, but reports of its prevalence have not usually evaluated random community samples, and validated questionnaires have not been used to elicit symptoms. The prevalence of specific colonic symptoms and the irritable bowel syndrome among representative middle-aged whites was determined from a defined population, and the impact of these symptoms on presentation for medical care was measured. An age- and sex-stratified random sample of 1021 residents of Olmsted County, Minnesota, aged 30-64 years, was obtained. All subjects were mailed a valid self-report questionnaire that identified gastrointestinal symptoms and functional gastrointestinal disorders. The response rate was 82% (n = 835). The age- and sex-adjusted prevalence of abdominal pain (more than six times in the prior year) was 26.2 per 100 (95% confidence interval, 23.1-29.2). The prevalence of chronic constipation (hard stools and straining and/or less than 3 stools per week greater than 25% of the time) was 17.4 (95% confidence interval, 14.8-20.0), whereas the prevalence of chronic diarrhea (loose watery stools, and/or greater than 3 stools per day greater than 25% of the time) was 17.9 (95% confidence interval, 15.3-20.5). The prevalence of abdominal pain and disturbed defecation was similar in women and men, except that infrequent defecation and straining at stool were more common in women. Using the Manning symptom criteria to identify irritable bowel syndrome (greater than or equal to 2 of 6 symptoms in those with abdominal pain more than six times in the prior year), the prevalence of irritable bowel syndrome was 17.0 per 100 (95% confidence interval, 14.4-19.6). Overall, 71 persons (9%) reported visiting a physician for abdominal pain or disturbed defecation in the prior year; a subset of variables related to pain severity were the best predictors of health care seeking after adjustment for age and gender. However, these accounted for only 22% of the log likelihood. In conclusion, more than one third of an unselected middle-aged population reported chronic abdominal pain or disturbed defecation, and more than one in six had symptoms compatible with the irritable bowel syndrome. Only a minority had presented for medical evaluation; moreover, the characteristics of the abdominal complaints did not explain the seeking of health care in most cases.