Irritable bowel syndrome is one of the most common gastrointestinal (GI) disorders. Within this large group of people, there is a small subgroup whose symptoms begin suddenly. It happens after what appears to be a bout of infection in the GI tract (gastroenteritis). How often do persons who suffer bacterial gastroenteritis develop IBS? Who gets post-infectious IBS and what causes the disorder? How is it treated? A review of the topic is presented.