 Colonoscopy has been widely accepted for the diagnosis and treatment of colon diseases. Properly performed, colonoscopy is generally safe, accurate, and well-tolerated. Diagnostic colonoscopy is the preferred method to evaluate the colon in most patients with large-bowel symptoms, iron deficiency anemia, abnormal results on radiographic studies of the colon, positive results on colorectal cancer CRC screening tests, post-polypectomy and post-cancer resection surveillance, and diagnosis and surveillance in inflammatory bowel disease. In addition, colonoscopy has been introduced for CRC screening in some Western countries e.g. in the United States and Germany. Recent trials showed that screening colonoscopy has a large potential for prevention and early detection of colorectal cancer. Diagnostic colonoscopy is usually combined with endoscopic resection of small and medium sized polyps and flat neoplastic lesions. Patients in whom larger lesions are detected at a diagnostic colonoscopy are usually rescheduled for therapeutic colonoscopy in an appropriate setting. 