Autosomal dominant hypophosphatemic rickets (ADHR) is an inherited disorder of isolated renal phosphate wasting, the pathogenesis of which is unknown. We performed a genome-wide linkage study in a large kindred to determine the chromosome location of the ADHR gene. Two-point LOD scores indicate that the gene is linked to the markers D12S314 [Z(theta) = 3.15 at theta = 0.0], vWf [Z(theta) = 5.32 at theta = 0.0], and CD4 [Z(theta) = 3.53 at theta = 0.0]. Moreover, multilocus analysis indicates that the ADHR gene locus is located on chromosome 12p13 in the 18-cM interval between the flanking markers D12S100 and D12S397. These data are the first to establish a chromosomal location for the ADHR locus and to provide a framework map to further localize the gene. Such studies will permit ultimate identification of the ADHR gene and provide further insight into phosphate homeostasis.