Acolonic polyp is a circumscribed mass of tissue that projects above the surface of the intestinal mucosa, which may be classified as either pedunculated or sessile, depending on whether or not it contains a discrete stalk, and according to the size and type. It has been believed that colorectal cancer evolves from a precursor lesion, the adenomatous polyp. The introduction of colonoscopy in the early 1970s, followed by the demonstration of the feasibility of colonoscopic polypectomy, provided the technology for the application of this concept to clinical practice. Colorectal cancer can be prevented through examination of the entire colon and identification of a polyp to be resected. According to the National Polyp Study in the USA, the incidence of colorectal cancer is reduced by 76~90% following colonoscopic polypectomy. Colonoscopy and polypectomy, when performed by adequately trained physicians, is a safe and effective procedure that can decrease deaths resulting from colorectal cancer.