Hidrotic ectodermal dysplasia (HED) or Clouston syndrome is a rare autosomal dominant disorder characterized by nail dystrophy, alopecia and palmoplantar hyperkeratosis, which maps to chromosome 13q11-q12.1. We confirmed linkage of HED to this region in a large French family. To define the critical region for HED, detailed haplotypes were constructed with new pericentromeric polymorphic markers. A recombination event in the family indicates that the HED locus maps centromeric to D13S1832. Our French family does not share a common haplotype with other pedigrees previously published (particularly French-Canadian), indicating that the mutations in these families are likely to be of different origin.