An epidemiological study conducted in 2003 in Europe in 8 countries with over 42 000 people, found on the basis of questionnaires a prevalence of 11.5% with a diagnosis of IBS of 4.8%.in the total population; the results of this study were comparable to data obtained in the USA. A French work of our team at 35 447 healthy adults found a 6.2% frequency. In all these studies, there is a very large predominance of women (sex ratio near 2), with a preponderance of subjects of the age group 40-50 years.