Clinically significant hemorrhage following colonoscopic polypectomy may occur primarily as the polyp is removed or manifest itself days to weeks later secondary to clot dissolution. The rate of hemorrhage following colonoscopic polypectomy ranges widely from 0.3 to 6.1 percent, depending on whether the data are derived from studies using the number of patients or number of polypectomies. A retrospective study was performed in our institution to study 4,721 patients who underwent polypectomy between January 1987 and December 1991. Twenty (0.4 percent) of these patients required hospital admission because of 9 primary and 11 delayed hemorrhages. Fifty-four polyps were removed from these patients: 11 in the right colon, 7 in the transverse colon, 17 in the descending colon, and 19 in the sigmoid colon. Eight polyps were 2 cm or larger, 10 were pedunculated, and 44 were sessile. Six patients underwent cauterization or resnaring of the bleeding polyp site, one patient underwent subtotal colectomy, and the remainder of the patients stopped bleeding spontaneously. Factors that could be associated with the outcome of hemorrhage include patient age, size, location, number and morphology of polyps (i.e., sessile or thick stalk), and use of anticoagulants. An experienced endoscopist with knowledge of electrosurgical and technical principles may be the most important factor for prevention of postpolypectomy bleeding.