Functional, or non-ulcer, dyspepsia (FD) is one of the most common reasons for referral to gastroenterologists. It is associated with significant morbidity and impaired quality of life. Many authorities believe that functional dyspepsia and irritable bowel syndrome represent part of the spectrum of the same disease process. The pathophysiology of FD remains unclear but several theories have been proposed including visceral hypersensitivity, gastric motor dysfunction, Helicobacter pylori infection and psychosocial factors. In this review, we look at the evidence, to date, for the role of visceral hypersensitivity in the aetiology of FD. (C) 2006 The WJG Press. All rights reserved.