The diplolepideous-alternate peristome, when most highly developed, has endostome segments attached to a basal membrane and positioned alternate to the outer exostome teeth, with cilia often present between the segments. This peristome type defines the Bryidae ( sensu Vitt et al. 1998), which includes four orders: the Bryales, Leucodontales, Hypnales, and Hookeriales, of which the latter three are mainly pleurocarpous in their growth form. Chloroplast (rbcL, rps4, and trnL-trnF) and nuclear (18S rRNA) gene sequences have been analyzed using the parsimony optimality criterion to elucidate relationships among the Bryidae. The analyses strongly support the paraphyly of the Bryidae, with the Splachnidae, and possibly the Orthotrichidae, having arisen from ancestors within the Bryidae. The Leucodontales, Hypnales, and Hookeriales form a monophyletic group, as do the pleurocarpous members of the Bryidae. However, the two pleurocarpous clades are not resolved as sister groups, although their non-monophyly is not supported by the bootstrap. The phylogenetic hypothesis provides a context in which to infer evolutionary transitions in some key morphological characters relating to the peristome and the transition from the acrocarpous to pleurocarpous growth forms.