Rectal carcinoma in 50% to 60% of cases is localized in the rectum and, if diagnosed early can be locally excised. The authors evaluated the diagnostic accuracy of the preoperative endorectal ultrasonography (ERUS) in the staging of rectal tumors and the usefulness of the method to assess patients' suitability for local excision. In the retrospective analysis, we analyzed 29 patients with rectal cancer. The depth of invasion into the rectal wall was assessed by ERUS and all patients were qualified for tumor excision with transanal endoscopic microsurgery (TEM). We analyzed overall accuracy of ERUS and the effectiveness of treatment. In the analyzed group, diagnostic accuracy of ERUS in assessing T1 carcinomas was 89.2%, sensitivity 92.3% and specificity 50%. Local excision with TEM was deemed to be curative in 86.2% patients with rectal tumors detected by ERUS. ERUS is an accurate method of preoperative assessment of T1 and T2 carcinomas and its diagnostic accuracy is sufficient to qualify patients for anal-saving operations.