Fetal urinary tract obstruction accounts for the largest identifiable cause of kidney failure in infants and children. The site of obstruction along the urinary tract varies from the ureteropelvic junction (UPJ), to the ureterovesical junction and urethra. Congenital obstructive lesions may be associated with abnormal renal development, resulting in renal agenesis, hypoplasia. The effects of urinary tract obstruction to impair nephrogenesis and to injure already-formed nephrons clearly compound perinatal risk factors as well as those accumulating throughout life. The role of angiotensin II in normal kidney development is well established, and numerous cases of renal maldevelopment and injury are reported in fetuses born to mothers exposed to angiotensin II inhibitors. The functional response of the fetal kidney to urinary tract obstruction depends on the location and timing of the obstruction. Numerous factors combine to determine the immediate and long-term impact of fetal urinary tract obstruction in affected infants.