One part of the operative procedure of radical hysterectomy (RH) is the dissection of the ureter from itsoverlying tissue and this may result in injury to the ureteric adventitia. This might induce ureteric obstructionand consequently produce hydronephrosis. The objective of this prospective study was to evaluate the incidenceof hydronephrosis after RH in patients with early stage cervical cancer. From July 2006 through March 2007,77 patients with IA2-IIA cervical cancer who planned to undergo radical hysterectomy and pelviclymphadenectomy (RHPL) received urinary tract ultrasonography 5 times (one day before surgery and 7 days,6 weeks, 3 months and 6 months after the operation) from one radiologist. Patients who had hydronephrosisbefore surgery, suffered intraoperative ureteric injury, or were lost follow-up at 7 days after surgery wereexcluded from the study. Urinary tract ultrasonography was performed on 77, 55, 52 and 52 patients at eachvisit. Right hydronephrosis was detected in 16, 7, 5 and 3 patients, and left hydronephrosis in 16, 11, 3 and 1 , at7 days, 6 weeks, 3 months and 6 months, respectively, after the operation. Hydronephrosis persisted in 8 patients(15%) after 3 months. Two of these had undergone exploratory laparotomy for lysis of ureteral adhesions. Onepatient who developed hydronephrosis had local recurrence and received further treatment with concurrentchemoradiation therapy. In conclusion, the incidence of persistent hydronephrosis over 3 months after RHPLwas 15%, even without intra-operative ureteric injury. However, only a few cases required surgical intervention.