Irritable bowel syndrome is a common functional gastrointestinal disorder that affects children and adults. The lack of consensus diagnostic criteria and pathophysiologic understanding has hampered clinical progress in diagnosing and treating this disorder. The recent development of the Rome diagnostic criteria, mapping of brain-gut pathways using neuroimaging, and serotonergic pharmacology have greatly advanced the field. Chronic and acute life stress, especially during childhood, has been recognized as central to the initiation of the disorder and the induction of acute symptoms. We propose a developmental continuum whereby the clinical presentation of irritable bowel syndrome changes with age from irritability during infancy, to diarrhea in toddlers, to recurring abdominal pain during school age, and to pain and altered bowel habits during later adolescence and adulthood.