Background: Endoscopic polypectomy is a standard method of treatment of gastrointestinal polyps, but is associated with substantial risk of complications. The most common is hemorrhage, the rate of which varied between 0.3%, and 6%. Various prophylactic techniques have been used to reduce this incidence. The aim of this study was to establish whether the prophylactic injection of adrenaline-saline solution reduces the risk of post-polypectomy bleeding in colonoscopic polypectomy. Methods: Between May 2000 and June 2002, patients with colorectal polyps of size greater than or equal to1 cm were randomized to receive submucosal epinephrine injection (group A) or no injection (group B). The polypectomies were carried out using the conventional method. In group A, epinephrine (1/10,000) was injected into the stalk or base of the polyp. The patients were observed for complications. Results: A total of 69 patients with 100 polyps were enrolled in this study: n = 50 in group A, and n = 50 in group B, according to randomization. There were a total of nine episodes of postpolypectomy hemorrhage, one in the epinephrine group and eight in the control group (1/50 vs 8/50, p < 0.05). The bleeding correlated with the size of the polyps and the diameter of the stalks. Conclusions: Epinephrine injection prior to colonoscopic polypectomy is effective in preventing bleeding.