The ODD locus was initially mapped to a 28 cM region of human chromosome 6q22-q24,17 which was subsequently refined to the 1.9 cM genetic interval delineated by the polymorphic markers D6S261, proximally, and D6S1639, distally.18 This study further indicated that ODD with associated neurological defects maps to this same interval. Recently, Paznekas and coworkers reported that the pleiotropic phenotype of ODD arises as the result of mutation of GJA1, the gene encoding the gap junction protein, connexin 43.19 In the current paper, we report nine different missense mutations, seven of which have not been described previously, in 10 unrelated families and confirm that type III syndactyly, at least in a subset of cases, is allelic with ODD. Using whole mount in situ hybridisation to analyse a developmental series of morphologically-staged embryos, we further demonstrate that there is a strong correlation between the sites of Gja1 expression and the clinical phenotype.