The spontaneous intraperitoneal rupture of the urinary bladder is an extremely rare and life-threatening event. Often, there are difficulties in establishing the diagnosis. A patient with spontaneous perforation of the urinary bladder, 17 years after successful treatment of an adenocarcinoma of the prostate by pelvic radiation therapy, is reported. Aspects of etiology, clinical presentation, diagnosis, and management are described. Early surgical exploration including primary closure of the defect, peritoneal lavage, and continuous vesical drainage were associated with a favorable outcome.