Recent advances in surgical and endoscopic treatments for rectal cancer demand more accurate preoperative assessment of both tumor localization and staging. Local resection or endoscopic polypectomy can be applied if there is reasonable certainty that no lymph node metastasis exists or that a tumor does not massively infiltrate the submucosa. The indications of laparoscopic colectomy are tumor infiltration limited to the submucosa and no evidence of lymph node metastasis. The differentiation between tumors confined to the intestinal wall and those with extramural infiltration also makes a difference in surgical planning, especially in the autonomic nerve-preserving operation. The purpose of this study was to assess the potential of endorectal MR imaging in defining the extent of colorectal cancers and to discuss the practical aspects of this procedure.