Bartter's syndrome is generally attributed to a primary defect in salt reabsorption either in the ascending limb of Henle's loop or in the proximal tubule. 2 siblings presented here have all the clinical and biochemical features of Bartter's syndrome but seem to have defective salt reabsorption in the distal convoluted tubule. A surreptitious use of diuretics was ruled out. Free water clearance was reduced in both patients and also was low after the addition of furosemide when compared with controls. Urine osmolalities following overnight dehydration were 883 and 1,000 mosm/l. The reduced maximal free water clearance argues against a proximal defect, and the normal urine concentration against a Henle's loop defect. Low free water clearance after furosemide suggests a defect in the distal convoluted tubule.