1. Four boys with classical nephrogenic diabetes insipidus have been treated by indomethacin, by hydrochlorothiazide, and by the combination of indomethacin and hydrochlorothiazide.
2. Hydrochlorothiazide treatment was slightly more effective than indomethacin treatment in reducing the urine volume and increasing the urine osrnolality.
3. The combination of indomethacin and hydrochlorothiazide appeared to be additive and especially helpful in infants and young children before the autonomy of drinking.