Endoscopy plays an integral role in the diagnosis, management, and surveillance of inflammatory bowel disease (IBD). Because there is no single pathognomonic test that establishes the diagnosis of IBD, endoscopy is useful in establishing the diagnosis, excluding other etiologies, distinguishing Crohn's disease from ulcerative colitis, defining the patterns, extent, and activity of mucosal inflammation, and obtaining mucosal tissue for histologic evaluation. In established IBD, endoscopy helps define the extent and severity of involvement, which in turn influences medical and surgical decisions, aids in targeting medical therapies, and allows for the management of IBD-related complications. Furthermore, endoscopy plays a key role in the surveillance of patients with long-standing colitis who are at increased risk for dysplasia and the development of colorectal cancer.