The radiotherapy panel met to develop international consensus about the optimal use of radiotherapy, alone or in combination with surgery and chemotherapy, in the radical treatment of patients with bladder cancer. A consensus meeting of experts in the treatment of bladder cancer was convened by the Société Internationale d'Urologie (SIU). The radiotherapy committee, which had international representation from 6 countries, performed a critical review of the English-language literature and developed evidence-based guidelines for the use of radiotherapy in the treatment of patients with bladder cancer. The strength of the evidence supporting each recommendation was ranked according to a 4-point scale. Consensus statements were developed that address (1) the effectiveness of radiotherapy in the treatment of bladder cancer, (2) the most appropriate patients for curative treatment with radiotherapy, (3) the optimal method of delivery of radiotherapy, (4) the best radiation prescription for treating bladder cancer, and (5) optimal management of the patient's condition after radiotherapy has been provided. Radiotherapy is effective treatment for selected patients with bladder cancer; it produces long-term disease control with preservation of normal bladder function. Modern radiotherapy treatment techniques offer the potential to improve cure rates and reduce adverse effects. All patients in whom the condition is newly diagnosed should be assessed in a multidisciplinary setting, where the relative merits of surgery, radiotherapy, and chemotherapy can be considered on an individual basis with the aim of optimizing overall outcomes.