Dyspepsia is a term encompassing several symptoms of the upper gastrointestinal (GI) tract, including acid reflux, heartburn, nausea, vomiting, and abdominal pain or discomfort. Up to 40% of the population suffer with dyspepsia; 5%–10% will consult their GP, and 1% will undergo endoscopic assessment. Over-the-counter medications cost patients £100 million annually, and prescribed drugs cost the NHS over £463 million annually. There is a steady rise in incidence with increasing age. Helicobacter pylori is present in 40% of the UK population, with many individuals acquiring the infection in childhood and remaining asymptomatic. It has been associated with peptic ulcer disease and distal gastric cancer. This chapter covers the approach to diagnosis, key diagnostic tests, therapies, and prognosis as well as dealing with uncertainty when it comes to the initial diagnosis.