A newly recognized causative factor in a subset of patients with irritable bowel syndrome (IBS) is called post-infectious IBS (PI-IBS). IBS symptoms frequently develop after an acute episode of infectious gastroenteritis. Several studies have been made in our understanding of the concept of PI-IBS. Recent studies suggest that transient or chronic gastrointestinal inflammation may play a role in IBS pathogenesis. PI-IBS can be regarded as a natural experiment model in which an insult in the form of an infective disease impacts on subjects with underlying genetic and psychosocial predispositions who then develop IBS. IBS is likely to be a complex trait wherein variability in clinical presentation is partially explained by heterogeneity in underlying genetic and environmental risk factors for PI-IBS. Further studies on PI-IBS are needed to understand the pathophysiology of functional gastrointestinal disorders and to develop new promising management for such patients.