external beam radiotherapy is consolidated like radical treatment for localized and locally advanced prostate cancer. in addition, more and more studies show its effectiveness as much in postoperative as in salvage intention. before choosing a therapeutic option, it is important to know the baseline state of the patients and the possible side effects of the treatment. in that way, different questionnaires and toxicity scales are at our disposal. acute effects, during the treatment and the following weeks, are due to irritating and inflammatory symptoms. chronic toxicity, months or years after radiotherapy, are consequence of the fibrosis and ischemia, as well as of alterations at the myogenic and neuronal level. urinary incontinence is a relatively uncommon symptom among patients who have been treated with radiotherapy. but, due to the profound impact on the quality of life of our patients, it is necessary to identify patients at higher risk. antecedent of transurethral resection of the prostate, before or after the irradiation, and severity of acute genitourinary toxicity increase the risk of developing incontinence.