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The preoperative staging of rectal cancer has important implications for treatment as local therapies become increasingly utilized. Seventy-seven patients underwent preoperative staging using endorectal ultrasonography. All patients had complete pathologic staging and none had preoperative radiotherapy. Depth of invasion of the tumor was accurately predicted in 75 percent of cases in the entire group, with 22 percent overstaged and 3 percent understaged. Accuracy improved greatly over the study period, and in the past six months, 95 percent have been accurately staged for depth of invasion with 5 percent overstaged. Lymph nodes have been properly classified into positive and negative groups in 88 percent of cases in the past year, with a specificity of 90 percent and a sensitivity of 88 percent. Endorectal ultrasound is an accurate preoperative staging modality. Accuracy is improved greatly with increased experience and it has been found that the 5-layer anatomical model facilitates accurate staging. Introduction of the ultrasound probe through a previously placed proctoscope ensures complete scanning of the entire lesion and should be used for the majority of examinations.