Medical students are taught that 90% of all diagnoses are made through careful assessment of the patients' symptoms. Clinicians now rely heavily on techniques such as endoscopy or radiology before making a definitive diagnosis of organic disease. Most gastroenterologists would require endoscopic confirmation before labeling a patient as having peptic ulcer disease and would make a diagnosis of Crohn disease based on small bowel radiology or colonoscopy. However, the most common causes of symptoms of the gastrointestinal tract are functional. It is important that clinicians obtain a thorough history so that the disorder of the patient can be accurately defined.