For the last 10 years, along with surgery, radiotherapy has become a major issue in the curative treatment of prostate cancer. Several radiotherapy techniques can be used. In good prognosis cancers, when the prostate is small, brachytherapy is one of the therapeutic options. By implanting radioactive seeds within the prostate, this technique permits strictly limited intraprostatic irradiation. Conformal external beam (3D) radiotherapy adapts to individual morphology according to dosimetric CT scan data. This is particularly useful to deliver a high dose in the target volume while limiting the dose in surrounding organs. It is indicated either for localised tumours as an alternative solution to surgery, or for tumours with more aggressive patterns or locally advanced that will in both cases require adjuvant hormotherapy; conventional (2D) radiotherapy can be used in case of isolated clinical or biological relapse after prostatectomy. These last two techniques induce two main types of late toxicity: radio-induced rectitis and sexual impotence. Last but not least, radiotherapy as well as nuclear medicine can be used with palliation intent and may be of great help to relieve pain in case of bone metastases.