The work-up conducted in order to reach a correct diagnosis based on a combined modality staging in patients with low risk rectal cancer, is presented. The diagnostic accuracy of each imaging technique is analyzed by the comparison of the radiologic TN with the histologic TN in 13 patients directly referred to surgery based on combined modality staging. Control with histologic findings has staged as T1-T2 13 patients directly referred to surgery, while only a patient was shown to have microinfiltration of perirectal fat. As for T, diagnostic accuracy was 90% for transrectal US, 66% for MRI, 61% for CT. Accuracy of transrectal sonography in the differentiation of T1 from T2 was 70% with a trend towards overstaging. None of the procedures has suggested the presence of metastatic lymph nodes while on histology small neoplastic foci were evidenced in a normal-sized perirectal lymph node. The high diagnostic accuracy of US in the definition of T in rectal cancer is confirmed. It is underlined that no procedure enables the detection of neoplastic microinfiltration of normal lymph nodes.