Up to 35% of the world population suffer from functional gastrointestinal disorders (FGD), accounting for about 40% of gastroenterologic and 12% of primary care practice. Society incurs high costs from FGD morbidity in terms of medical workups and absenteeism from work. FGD are characterized by chronic and recurrent symptoms of the gastrointestinal (GI) tract without detectable structural or biochemical abnormalities. In the absence of universal biologic markers, the diagnosis is based on consensus symptom criteria (1). This chapter reviews current knowledge of the pathophysiology and provides a practical approach to patients with functional dyspepsia and irritable bowel syndrome, 2 of the most common functional GI syndromes.