The authors stress the value of the routine use of endorectal US for the preoperative staging of rectal cancer. This method accurately demonstrates the exact level of the lesion, the degree of circumferential invasion, the depth of local involvement and the extent of eventual spread beyond the rectal wall, the invasion of the surrounding structures and the presence of enlarged perirectal lymph nodes. A hundred and forty-one patients with rectal carcinoma located 3-16 cm from the ano-cutaneous line were examined with endorectal US preoperatively; a comparison was made between US findings and pathological data, so that a correlation could be made between US (uT) and histologic (pT) findings. A radial probe and a 7-MHz transducer were employed. Our results show US accuracy to be 93.6% with only 4 cases of understaging and 5 of overstaging. A hundred and twenty-nine patients who had undergone major surgery were also studied to evaluate US accuracy in lymph node detection: in 110 cases the actual lymph node status was correctly demonstrated; US diagnostic accuracy was 85.3% with 16 false positives and 3 false negatives. The correct evaluation of the actual local tumor spread, as demonstrated by endoluminal US, allows the choice of the correct treatment, together with a personalized therapeutic schedule, to reduce the incidence of local recurrences and to save, whenever possible, sphincter functionality.