The growing frequency of prostate cancer discovered at a localized stage, about 20% of which are treated by radiotherapy, justifies an analysis of the adverse effects of this treatment modality. The risks of impotence and gastrointestinal and urinary irritative disorders after radiotherapy are well known. The objective of this article is to review the less well known risks of radiation-induced tumours based on the data of the literature and to discuss possible modifications of the conventional modalities of follow-up. The risk of radiation-induced tumours is well known in gynaecology, but the link is more difficult to establish after radiotherapy for prostate cancer. The most recent series report an increased relative risk of bladder cancer (RR = 1.63) and rectal cancer (RR = 1.6 to 1.7): the risk of second tumour is 15% at 5 years in the irradiated population and 34% at 10 years. Finally, although follow-up is still too short, new conformal radiotherapy techniques do not appear to decrease this risk. These data indicate the need for caution in patients combining several risk factors, such as smoking for bladder cancer and bladder and rectal endoscopic surveillance for more than 5 years should be proposed in patients treated by radiotherapy for prostate cancer.