Rather than being a diagnosis of exclusion, irritable bowel syndrome (IBS) is a diagnosis that can be identified by symptom-based criteria. The collection of these criteria by a meticulous history can be enhanced by using various tools. Once a positive diagnosis is made, using clinical criteria for diagnosis, one should look for alarm or warning symptoms or signs, and should characterize the type of bowel habit. Determining whether the condition is a diarrhea-predominant or a constipation-predominant IBS will direct further diagnostic evaluation and management.