Urological complications, essentially bladder outflow obstruction and hydronephrosis, are caused by the local extension and lymphatic spread of prostate cancer. Although bladder outflow obstruction is a very common finding at diagnosis, results from clinical studies have revealed that it is not a prognostic factor for response to androgen blockade. Hydronephrosis has been shown to have an independent prognostic value for progression after hormonal treatment and correlates also with time to death from prostate cancer. Furthermore, persistent or newly developed hydronephrosis during treatment also predicts a shorter time to progression. The incidence of bladder outflow obstruction is significant in advanced prostatic cancer and may be a source of morbidity, which will impact on the patient's quality of life. Decompression of ureteric obstruction in hormone-refractory cancer decreases the length of hospital stay, thereby improving quality of life. Finally, hydronephrosis, but not bladder outflow obstruction, can be considered to be an independent prognostic variable for the response to androgen blockade. This paper reviews the incidence of urethral and ureteric obstruction in patients with advanced prostate cancer, evaluates the prognostic significance of these urinary complications and discusses the therapeutic strategies available for treating patients with this disease.