Vesico-ureteric reflux (VUR) is one the most common inherited disorder in humans. Even though this defect is common among siblings and parents of index patients (27-40%), the mode of inheritance is not well defined. Parents and siblings (three female and two male) of a 13-year-old girl with end-stage renal failure (ESRF) due to reflux nephropathy were screened for VUR although they had not presented episodes of urinary tract infection. VUR was identified in the father (44 years old) and in all the three sisters (aged 15 years, 16 years and 18 years) while the two brothers (aged 5 years and 8 years) had normal renal ultrasonograms and cystograms. A technetium-99m di-mercapto-succinic acid ((99m)Tc-DMSA) scan demonstrated renal scars in the father and in two of the sisters with VUR. No episodes of urinary infection had been documented for any relatives. Haplotype analysis on the X-chromosome confirmed paternity. This is the first description of VUR compatible with an X-dominant trait. This mode of inheritance must be added to what is already known on familial VUR, and future studies should also consider this possibility.