Toward greater resolution of the phylogeny of the Rosaceae, we analyzed 19 genera representing the major clades as well as isolated genera. We used three nuclear genes (two copies of the granule-bound starch synthase, polygalactonuonase inhibitor proteins, and polyphenol oxidases) and four chloroplast genes (matK, ndhF, rbcL, and trnL). The combined dataset was analyzed using maximum parsimony, maximum likelihood, and Bayesian approaches. Parsimony analyses support a sister-group relationship between Rosoideae (narrowly defined with base chromosome numbers of 7 or 8) and the remainder of the family. Nitrogen-fixing genera (redefined tribe Dryadeae) form a clade that is weakly supported as sister to the remaining members of the family outside the Rosoideae in parsimony or to Rosoideae in maximum likelihood and Bayesian analyses. All analyses show very strong support for six clades in addition to Dryadeae and Rosoideae. Kerrieae, Neillieae, and Spiraeeae are as traditionally defined. Gillenia is strongly tied to Maloideae, broadly circumscribed to include Kageneckia, Lindleya, and Vauquelinia, which do not have pome fruits. Instead they share the potential synapomorphy of x=17 with traditional members of this subfamily. Amygdaloids Exochorda, Oemleria, and Prinsepia form a clade to the exclusion of Prunus. The final clade has Adenostoma, traditionally placed in its own tribe, united with Chamaebatiaria, Sorbaria, and the Asian Spiraeanthus. Short internal branches in the tree may suggest a rapid radiation early in the history of the family.

Key words: Amygdaloideae, Maloideae, nucleotide sequence data, Rosaceae, Rosoideae, Spiraeoideae