The neonatal form of Bartter syndrome is characterized by intrauterine onset of polyuria leading to severe polyhydramnios. We report a patient with the early onset of the syndrome and a similar history in a previous sibling who died in early neonatal life. The patient is a female product of 33 weeks of gestation complicated by severe polyhydramnios. Her birth weight was 2,100 g. Polyuria led to severe dehydration on the 3rd day of life. Laboratory studies showed hypokalemia, hyponatremia, and elevated plasma levels of renin and aldosterone. Hypercalciuria was associated with echographic evidence of nephrocalcinosis. Indomethacin therapy resulted in a significant reduction in urine volume and correction of biochemical abnormalities. Growth and development are satisfactory after 4 years of indomethacin therapy, but nephrocalcinosis remains unchanged.