The traditional Urticales (Ulmaceae, Celtidaceae, Cannabaceae, Moraceae, Urticaceae, and Cecropiaceae) is one of the more controversial orders in terms of family circumscriptions and both inter- and intra-familial phylogenetic relationships. Recent molecular evidence has clarified its position as a monophyletic assemblage within a now expanded Rosales, with close relationships to an unresolved group including Barbeyaceae, Dirachmaceae, Rhamnaceae, and Elaeagnaceae. Although the Ulmaceae has now been demonstrated to be sister to the rest of the urticalean lineage with both morphological and molecular data, the circumscription and relationships of the other families has remained unclear and controversial. The majority of morphological analyses have concluded either that (1) Celtidaceae, Cecropiaceae, Moraceae, and Urticaceae should be combined as one family, or (2) at least Moraceae and Urticaceae should be merged; the placement of Cannabaceae being largely unknown. Analyses now based on rbcL, ndhF, and trnT-trnL spacer sequences strongly support monophyly of each of the families Moraceae and Urticaceae (with Ceropiaceae) and the polyphyletic nature of Cecropiaceae with Poikilospermum at least imbedded within Urticaceae. There is both strong sequence and indel support for the placement of Cannabaceae within Celtidaceae. The different molecular data are congruent in indicating polyphyly for the tribe Moreae and the isolated position of Maclura within Moraceae, and that a number of tribes within Urticaceae are either paraphyletic or polyphyletic. Some of this discrepancy is due to the unusual placements of some Hawaiian Urticaceae, most notably Touchardia. The robust molecular results for major portions of the phylogenetic history of the urticalean clade permit reinterpretation of morphological, anatomical, and ecological features in the group as well as suggest changes in classification and nomenclature.

Key words: Cannabaceae, classification, ndhF, trnT-trnL, Urticaceae, Urticales