Bowel involvement of endometriosis often presents as partial obstruction in mensturally active women. However, mucosal involvement of endometriosis in the form of typical adenomatous polyp with stalk is extremely rare. This lesion as we called "endometriotic polyp", should be included in the differential diagnosis of colonic polyps. This case ie a 44 years old woman who has had a three years history of "hemorrhoid". She presented obstruction symptoms and signs with palpable polypoid masses in the rectum. The operation revealed massive adhesion and endometriomas in pelvic cavity and sigmoidrectum with scattered endometriotic nodules on the serosa. Radical resection of sigmoid and rectum together with hysterectomy under an impression of rectal cancer was performed. Pathologically, rectum was stenosed, and the mucosal surface showed multiple polyps with definite stalks, ranging in size from 0.8cm. to 2.0cm. in diameter as shown in Fig. 1. The wall of the involved rectum was thickened diffusely to measure up to 2cm. No ulceration or hemorrhage was present. Microscopically, sections from various parts of the rectum showed small and large foci of endometriosis. The endometriotic tissue consisted of microcystic glands and abundant dense stroma, and is well defined from surrounding intestinal structure. The endemetrial tissue was stained blue with Masson's trichrome and was in strong contrast with smooth muscle. Endometriotic foci was seen transmurally including submucosa and muscularia externa. Sections from mucosal polyps showed intact colonic epithelial covering and underlying endometrial manses comprising the most portion of core of the polyps.(Fig.2-4) The endometrial glands in polyps showed focal cystic dilatation. No ulceration of the covering epithelium was seen.