Adjuvant combined radio-chemotherapy in rectal cancer is indicated in stage UICC II and III (pT3/4 and/or pN+) without distant metastases (exception: resectable metastases of the liver). Radiotherapy alone improves local control in the pelvis. A statistical significant improvement of survival is only achievable in combination with systemic chemotherapy. In Germany neo-adjuvant, conventional fractionated radio-chemotherapy over five weeks is applied in patients with surgically inoperable tumors to achieve a "down-staging" with improvement of resectability. Neo-adjuvant radiotherapy of operable rectal cancer in five fractions of high single doses within one week has revealed a statistical significant improvement of survival if compared to surgery alone in the Swedish rectal cancer trial, but is not standard in Germany yet. The influence of technical advances in surgery as total mesorectal excision (TME) on indications of adjuvant therapy is evaluated in prospective randomized studies at this time.