The irritable bowel syndrome (IBS) is the most common chronic functional gastroenterological disorder both in adults and in children. In this study we evaluate the different aspects of this syndrome, comparing our observations on 332 children with other studies. Epidemiological data (frequency, sex, age) are examined so as the family histories of gastroenterological disorders. We take in account several pathogenic hypotheses, especially with reference to the alterations of gastrointestinal motility, which could be caused by several factors (psychological, prostaglandins, bile acids, etc.). The clinical picture is very variable, variations depending on the age of children and on the time of onset of IBS. The colic of neonate, caused by retention of air, is the main symptom in the first months of life, followed by chronic diarrhoea, also defined as toddler's diarrhoea, sometime alternating with constipation. In later childhood, recurrent abdominal pain represents a common complaint, in association with diarrhoea or constipation. The principal steps for a proper diagnosis so as the main differential diagnosis are defined. We explain the most important features of management (reassuring parents, free diet), excluding prescription of drugs, that produce only a transitory and symptomatic relief, so as elimination diets, that cause only a failure to thrive without any improvement of symptoms.