CT-scans were performed in the follow-up of 124 patients surgically treated for rectal carcinoma. CT allowed direct visualization of possible local recurrences and infiltration of neighbouring structures chiefly muscles and bones; it can also prove post surgical abscesses, metastatic spreads to lymph nodes and other structures such as liver, lung and bones; many of these lesions cannot so quickly and safely be demonstrated by other investigations. CT is also very helpful in radiation therapy planning. A CT guided percutaneous fine-needle aspiration biopsy can discriminate post surgical fibrosis from initial recurrences.