Five neonates with gross obstructive uropathies diagnosed in utero were operated during the first few days of life. Follow-up studies of up to 2 years postoperatively showed normal development of all the children. Radiologic investigations showed no obstruction and normal growth of renal parenchyma in all but one case, thus differing markedly from infants with gross obstructive uropathies who were diagnosed and referred to us some months after birth. The importance of prenatal diagnosis and hence early post partum treatment of obstructive uropathies appears to us proven.