It is evident that colorectal cancer screening programs have contributed to a decrease in mortality [1–3]. Since professional groups, especially gastroenterologists, generally prefer colonoscopy as the most effective tool for colorectal cancer prevention [2], a considerable proportion of people with adenomatous polyps are discovered at the time of screening. Accordingly, a large number of people require post-polypectomy surveillance, which places a huge burden on medical resources [4, 5]. Recent data showing that 20% of colonoscopies performed in practice were for surveillance after polypectomy [6] indicate the importance of appropriate allocation of medical resources. Therefore, efficient and safe guidelines on surveillance colonoscopy are needed to decrease the cost, risk and over-use of colonoscopy. Before the 1990s, because there was no available guidelines, annual follow-up colonoscopy was common practice after polypectomy. The National Polyp Study, showing that it was safe to defer the first follow-up colonoscopy for 3 years [7], raised the issue of the cost and burden of postpolypectomy surveillance, and eventually led to develop a guideline in 1997 that recommended a 3-year interval of colonoscopy after removal of adenomas [8, 9]. In 2003, the updated guideline recommended extended intervals of surveillance colonoscopy and introduced the concepts of risk stratification according to the results of index colonoscopy [10]. The observations of Atkin et al. [11] using sigmoidoscopy over 3to 6-year intervals showed that persons with adenoma of less than 1-cm size and with no high-grade dysplasia were not at a higher risk for developing colorectal cancer. This data clearly showed that patients could be stratified into low-risk or high-risk groups according to the size of adenoma in index colonoscopy. Based on these observations, the guideline published in 2003 recommended the first follow-up colonoscopy after 5 years for low-risk patients [10]. In 2006, the updated guideline further emphasized risk stratification at index colonoscopy to encourage a shift from intense surveillance to surveillance based on risk [12]. Recent guidelines recommend the first follow-up colonoscopy after 3 years in people at high risk (three or more adenomas, high-grade dysplasia, villous features, or an adenoma 1 cm or larger in size). Follow-up colonoscopy after 5–10 years is recommended for people at lower risk who have one or two small (\1 cm) tubular adenomas with no high-grade dysplasia. Surveillance examination for hyperplastic polyps was first included in a 2006 guideline, and 10-year follow-up evaluation is recommended. However, recent surveys have shown that a large proportion of clinicians do not follow the recommended guidelines. One national survey of surveillance colonoscopy after polypectomy in 1999 and 2000 showed that 54% of gastroenterologists and 86.5% of general surgeons recommend surveillance examinations every 3 years or even more often for a small adenoma [13]. For a hyperplastic polyp, 24% of gastroenterologists and 54% of surgeons recommend surveillance. Another national survey in 2004 showed that 61% of primary care physicians (family medicine and internal medicine) recommend surveillance for a hyperplastic polyp after 5 years or less, and 71% recommend surveillance for a single tubular adenoma after 3 years or less [14]. A recent self-reported patient survey showed that 46.7% of subjects with one or two nonadvanced adenomas received a surveillance colonoscopy S. P. Hong W. H. Kim (&) Department of Internal Medicine, Institute of Gastroenterology, Yonsei University College of Medicine, 250 Seongsanno, Seodaemun-gu, Seoul 120-752, Korea e-mail: kimwonho@yuhs.ac