A precise knowledge of the depth of invasion of tumor is essential for the planning of treatment of rectal cancer. Transrectal ultrasonography is a new diagnostic modality that has become useful in determining the depth of invasion preoperatively and the presence or absence of metastatic lymph nodes. Transrectal ultrasonography was used in preoperative staging of 36 patients with rectal cancer. Thirty three patients had a radical resection (17 low anterior resection, 15 abdominoperineal resection and 1 pelvic exenteration), one patient had a local excision. Two among these thirty four patients had preoperative radiotherapy. Preoperative transrectal ultrasonographic staging was compared with pathologic findings. In staging depth of invasion, the overall accuracy was 88.8 percent, overstaged in 5.8 percent, understaged in 5.8 percent. Transrectal ultrasonography is the more accurate method than CT in staging of depth of tumor invasion (61.8% vs 88.8%). In staging of lymph nodes, the overall accuracy of transrectal ultrasonography was 85.3 percent, sensitivity was 71.7 percent and specificity was 88.8 percent. Transrectal ultrasonography is a safe, inexpensive and accurate staging method in the assessment of both depth of invasion and nodal status.