Background: We report on two siblings with a new congenital tubulopathy presenting after normal pregnancy with distinct hyperchloriduria(up to 29 meq/kg×d) and hyperkaliuria (up to 17 meq/kg×d) and hypernatriuria. Distal tubular chloride reabsorption was extremely low (0.25). Increased prostaglandin synthesis, hyperaldosteronism, impaired renal concernating ability and normal calcium metabolism were found. Subjects: Two newborn siblings. Interventions: The effects of indomethacin, spironolacton and captopril on symptoms, electrolyte wasting, prostaglandin synthesis, activation of renin-angiotensin-aldosteron-system and concentrating ability were studied. Results: In spite of persisting elevated prostaglandin synthesis, captopril decreased electrolyte wasting, polyuria and hyperaldosteronism most effectively. Conclusions: The extremely decreased chloride reabsorption suggests a tubular defect similar to“classic” Bartter syndrome with severe symptoms occuring already in the neonatal period.