Dent's disease is a familial proximal renal tubular disorder which is associated with low molecular weight proteinuria, hypercalciuria, nephrocalcinosis, kidney stones and renal failure. The mode of inheritance and the primary defect for this disorder are unknown. An analysis of 5 unrelated British families revealed a greater disease severity in males and an absence of male to male transmission. This suggested an X-linked inheritance and we investigated this further by linkage studies in 33 members (12 affected, 21 unaffected) from two 3-generation families. Twenty X-linked polymorphic markers were used and linkage was established with the Xp11 loci ARAFI, DXS426, DXS255 and DXS988 with peak LOD scores and recombination fractions (theta) of 5.42 (theta = 0.000), 3.61 (theta = 0.000), 5.48 (theta = 0.000) and 4.25 (theta = 0.045) respectively. In addition, DXS255 revealed a microdeletion in the affected members of one family, thereby further localising Dent's disease to Xp11.22. Combined multilocus linkage analysis and deletion mapping studies defined the locus order Xpter-MAOB-(ARAFI, DXS426)-SYP-TFE3-(DXS255, DENT'S)-DXS988-Xcen, thereby mapping the microdeletion associated with Dent's disease to a 4 centiMorgan interval flanked by TFE3 and DXS988. Thus, Dent's disease is an X-linked disorder which is associated with a microdeletion of Xp11.22, and a further characterisation of this gene will help to elucidate the factors controlling proximal renal tubular function and the development of kidney stones.