The most common form of genetic nephrogenic diabetes insipidus(NDI), a rare inherited disorder, is congenital and is transmitted in an X-linked recessive mode. It is refractory to the antidiuretic effect of normal to moderately increased levels of plasma arginine vasopressin(AVP) but, in some cases, may respond to high levels of the hormone or its analogue, deamino-D-arginine vasopressin(DDAVP). X-linked congenital NDI has now been linked to over 128 different mutations in diverse coding regions of the AVP receptor 2(AVPR2) gene. The functional effects of these mutations vary from complete loss of responsiveness to a simple shift to the right in the dose response curve. We report a case of congenital partial NDI, with transversion of A to G at codon 280 of the AVPR2 gene, resulting in a subsequent change of amino acid from tyrosine to cysteine, and that has been effective with hydrochlorothiazide and high dose of DDAVP.