Clinical trials and registers data for quality assurance have been mandatory to achieve the good results and the enormous evolution which has been involved in rectal cancer surgery during the past 20 years. The whole business came into focus when local recurrences were considered as a matter of tumour biology and radiotherapy was introduced in many countries as a standard treatment in rectal cancer patients to reduce the local recurrence rate and to improve survival. During the last 30 years more than 8000 patients have been randomized in trials using pre- or post-operative radiotherapy. Those data are summarized in two good meta-analyses. In short, a summary of those meta-analyses has shown that radiotherapy reduces the local recurrence rate with 50%. Moreover, it has been revealed that pre-operative radiotherapy is better than post-operative radiotherapy in attempt to reduce the local recurrence rate and finally that there is a survival benefit with this reduction of the local recurrence rate.