Nucleotide variation of the internal transcribed spacer 2 region of nuclear ribosomal DNA was used to estimate the phylogeny of the moss family Hylocomiaceae. Both parsimony and neighbour-joining analyses support the monophyly of this family, as well as all seven of the genera within the family. Rhytidium appears as the basal taxon and a North American clade comprising Rhytidiopsis and Thelia is indicated. The analyses suggest that Hylocomium s. l., a polyphyletic genus, should be divided into three separate genera. The rate of nucleotide substitutions of the ITS-2 region in the Hylocomiaceae is consistent with the hypothesis of a molecular clock based on a relative rate tests. A nearly constant rate of 6.42 × 10—10 substitutions per site and per year is postulated for the family, a rate close to that of the Winteraceae and slower than that of Lopezia.