DNA sequence data from nuclear ribosomal internal transcribed spacer, including the 5.8s coding region, and plastid trnK/matK were used to reconstruct the phylogeny of Montieae (Portulacaceae), and a revised classification for the group based on monophyly is proposed. Montieae consists of the sister clades Claytonia and Montia. In Claytonia, there is strong support for the following clades: section Limnia, all annuals except the perennials C. sibirica and C. palustris; section Rhizomatosae, high elevation or high latitude perennials with rhizomatous or caudicose growth habits; and section Claytonia, species with spheric or obconic underground perennation structures. All analyses recover clades of Montia circumscribed as sections Montiastrum, Australiensis, and Montia. Heenan's Australasian Neopaxia is placed robustly in Montia section Australiensis, a clade limited primarily to Australia and New Zealand. DIVA and MacClade reconstruct the ancestral area for Montieae as western North America. Beringian taxa of Claytonia section Rhizomatosae are derived from low latitude western North American ancestors adapted to persistently wet, alpine habitats. Although we infer that section Claytonia had multiple shifts to northern high latitudes and potentially to eastern North America from western North America, relationships among clades in this section have limited support. Habitat reconstructions show that the pleisiomorphic condition for moisture regime in section Claytonia is largely maintained over shifts in elevation/latitude.