BACKGROUND Nephrogenic diabetes insipidus (NDI) is a disease characterized by a defective response to the antidiuretic hormone (ADH) of the renal collecting duct leading to a decline in the ability of the pro-urine concentration. METHODS A 23-year-old man presented with an over 20-year history of polyuria concomitant with hydronephrosis. The diagnosis of NDI was established by gene analysis as well as a water-deprivation and vasopressin test. All exons of arginine vasopressin V2 receptor (AVPR2) gene were amplified and sequenced. A novel hemizygous intragenic inframe deletion, cDNA 255th bp to 263th bp in exon 2 of AVPR2, was identified. These relevant translations from the 85th amino acid Asp to 88th amino acid Val were missed and replaced by amino acid Glu. After treating the patient with hydrochlorothiazide, his symptoms improved significantly. CONCLUSIONS The genetic analysis revealed a novel X-linked intragenic inframe deletion, AVPR2 gene cDNA 255th bp to 263th bp, causing NDI.