Irritable bowel syndrome (IBS) is common and affects 5 to 20% of individuals worldwide. Physicians with various specialties and at different settings are bound to meet these patients. This book is written by clinicians with long experience with IBS patients at different settings that have performed active research on IBS from different angles. Topics discussed include the prevalence and incidence of IBS worldwide, symptoms and consequences for patients and the society; IBS symptom based diagnosis; pathogenesis and the different possible aetiological factors; a new hypothesis for the pathogenesis of IBS; post-infectious and inflammatory bowel disease (IBD) associated IBS and treatment options, both non-pharmacological and pharmacological. This book does not only contain up to date data, but also included are the authors' points of view and their argument in several debated issues in IBS.