Irritable bowel syndrome (IBS) is a cluster of abdominal complaints frequently encountered in the primary setting. It is the most common gastrointestinal complaint seen in primary practice and accounts for 50% of referrals to gastroenterologists. Although the pathology of the disease currently is unclear, the diagnosis is not one of exclusion. When confronting this clinical syndrome of abdominal pain, bloating, flatulence, and changes in bowel habits, the clinician is called upon to balance the need to rule out organic causes with the expense and risk of testing. Optimally the clinician can use established guidelines that clarify the most efficient approach to diagnosing and treating IBS, while providing the patient with the reassurance and education needed to deal with this chronic disease. This article deals with the pathophysiology, diagnosis, and management of IBS.