Mutations in genes encoding chloride transporters cause Bartter's syndrome. An antenatal form associated with salt wasting and deafness has been observed in persons with mutations in BSND, the gene encoding barttin, a protein controlling the membrane insertion of two distinct chloride transporters. This report describes a child with the syndrome yet a normal BSND gene. The child had mutations in each of two genes encoding the chloride transporters ClC-Ka and ClC-Kb. The data provide strong evidence that barttin regulates ClC-type chloride channels and thus provide new insight into renal salt handling.