Dyschondrosteosis is an autosomal dominant form of mesomelic dysplasia that is often combined with a deformity of the forearms called Madelung deformity. Based on the observation of X-Y translocations (p22,q12) in patients with dyschondrosteosis, the authors tested the pseudoautosomal region in eight affected families and showed linkage of the dyschondrosteosis gene to a microsatellite DNA marker at the DXYS233 locus (Zmax = 6.26 at theta = 0). Since the short stature homeobox-containing gene (SHOX) involved in idiopathic growth retardation and possibly Turner syndrome maps to this region, SHOX was regarded as a strong candidate gene for dyschondrosteosis. This article reports the detection of large-scale SHOX deletions in seven of the eight families and a nonsense mutation of SHOX in the remaining family affected with dyschondrosteosis. Additional evidence suggests that Langer mesomelic dwarfism results from homozygous mutations at the genetic locus responsible for dyschondrosteosis.