In a survey of patients with inflammatory bowel disease (IBD), colonoscopy with multiple biopsies has been shown to be superior to either colonoscopy alone or barium studies in assessing disease extent. Thus, of a total of 149 patients, 23 (15%) were considered to have total colitis on barium enema, 51 (34%) on macroscopic colonoscopy appearance compared to 92 (62%) on biopsy. Furthermore, radiological assessment of "skip lesions" was shown to be unreliable. Although it remains to be seen whether the more accurate delineation of disease extent achieved by endoscopy is advantageous in terms of clinical management, it may have implications for our understanding of the disease.