Irritable bowel syndrome (IBS) is a commonly encountered condition seen in multiple medical specialties. Recent research has brought dramatic advances in our understanding of the epidemiology, burden of illness, diagnosis, and management of IBS. It is now widely accepted that the prevalence of IBS is between 10% and 20% of the US population and that the direct and indirect costs associated with IBS are significant. The processes required for diagnosis of IBS remain controversial. Scant evidence exists to support exhaustive diagnostic evaluations, and IBS is no longer considered a diagnosis of exclusion. The use of standardized symptom-based criteria remains to be perfected, and the diagnosis is often arrived at only after multiple laboratory, endoscopic, and radiologic examinations. The effects of treatment for IBS mirror the heterogeneous nature of the condition. No single medication has proven to be universally effective, and multiple therapeutic approaches exist. Greater understanding of gastrointestinal neurophysiology has led to promising advances in medical and nonmedical approaches to IBS.