To evaluate the validity of rectal endoscopic ultrasonography (EUS) in the staging of rectal cancer, EUS was performed preoperatively in 31 patients with a rectal carcinoma confirmed by endoscopic biopsy, and the results were compaired with the histological depth of the tumor infiltration and the metastasis of adjacent lymph nodes in resected specimens. 1) In assessing the depth of tumor invasion, the overall accuracy rate of EUS was 83.9%, overstaging rate 6.5%, understaging rate 9.7%. 2) In assessing the metastasis of adjacent lymph nodes, the overall diagnostic accuracy rate of EUS was 71.0%, positive predictive value 80.0%, negative predictive value 66.7%, diagnostic senstivity 53.3%. In conclusion, EUS will become an important diagnostic procedure for staging of rectal cancer with the combined use of transcutaneous abdominal ultrasonography or abdomimal computed tomography.