Prenatal ultrasound has set the stage for new trends in the diagnosis and treatment of many urinary tract malformations, in particular duplication of the renal collecting system with ureterocele. The authors have reviewed their experience with 41 ureteroceles in 7 years. The 36 patients were divided into two groups: those with prenatal diagnosis and subsequent early treatment (group A, 14 cases), and those with diagnosis later after birth (group B, 27 cases) showing various degrees of renal impairment as assessed by a 99Tc-diethylenetriamine pentaacetic acid scan. The surgical approach carried out on the patients of each group with particular regard to the endoscopic incision of the ureterocele as the treatment of choice, especially in neonatal period, is discussed.