Based on recent epidemiologic studies of functional intestinal disorders, we have attempted to answer the following two questions: a) what is the prevalence of functional intestinal disorder in the Western world, b) are there epidemiologic variations in the different modes of symptomatic presentation of functional intestinal disorders? The overall prevalence of functional intestinal disorders in the Western world ranges between 17 and 23 percent according to the country considered, and is between 14 and 18 percent for the irritable bowel syndrome and 4 to 8 percent for painless constipation. The "irritable intestine" group is characterized by a sex ratio of close to one, a median age near 40, a strong influence of stress on symptoms, and the frequency of complaints such as nausea, vomiting, migraine, and pyrosis. The syndrome is seen in active subjects, who believe that they are "sick", and as such, seek medical advice often. Anxiety and depression are frequently encountered. Patients are often athletes, smokers, and have diarrhea. On the other hand, "painless constipation" is characterized by a high prevalence of women and age over 50. Often these subjects do not have any active professional activity. Stress-related and extradigestive symptoms are rare. They do not consider themselves "sick" and do not seek medical advice very often. Conversely, they use laxatives frequently. Individualization of epidemiologically different groups suggests that the pathophysiology may differ between the two groups and perhaps that there are specific therapeutic and diagnostic approaches accordingly.