Congenital anomalies of the kidney and urinary tract (CAKUT) are regarded as a single entity. The degree of obstruction may have an additional influence on the parenchymal malfunction. Congenital dilatation of the upper urinary tract associated with symptomatic urinary tract infection must be treated early with intensive antibiotic therapy. In some cases temporary urinary diversion is also required. Further diagnostic procedures are then postponed in such cases. In all other cases of dilatation of the upper urinary tract diagnosed prenatally or early in the postnatal period, diuresis renography is still the cornerstone of diagnosis, even though it has definite limitations in young infants and in babies with poor kidney function. Functional gadolinum MR-urography will become the method of choice in the near future, since it combines good functional and excellent morphological presentation. When an obstruction hampering function is definitely present surgical correction is indicated: open and endoscopic surgery yield similarly good results. Molecular markers in CAKUT may soon be used as prognostic indicators. Examination of the molecular alterations that occur in renal and urinary tract anomalies may also lead to medicamentous protection of renal function.