Published phylogeny reconstructions of the palm family (Arecaceae) are based on plastid DNA sequences or restriction fragment length polymorphisms (RFLPs), nuclear DNA sequences, morphological characters or a combination thereof, and include between 33 and 90 palm species. The present study represents all previously recognized subfamilies, tribes and subtribes of palms and 161 of the 189 genera. The plastid DNA region matK was sequenced for 178 palm species and ten commelinid monocot outgroup species, and was combined with new and previously published plastid DNA sequences of trnL–trnF, rps16 intron and rbcL. The addition of matK sequences and more taxa resulted in a highly resolved and largely well-supported phylogeny. Most importantly, critical basal nodes are now fully resolved and, in most cases, strongly supported. On the basis of this phylogeny, we have established a new subfamilial classification of the palms, in which five subfamilies are recognized, rather than the six that were included in the previous classification. The circumscriptions of the subfamilies Calamoideae and Nypoideae were corroborated. The phylogeny supported a new circumscription for the subfamily Coryphoideae, including all taxa previously recognized in Coryphoideae with the addition of the tribe Caryoteae, formerly of the subfamily Arecoideae. The phylogenetic analysis also supported a new delimitation for the subfamily Ceroxyloideae that contains the tribes Cyclospatheae and Ceroxyleae, and all genera formerly included in the subfamily Phytelephantoideae, but excludes the tribe Hyophorbeae. Finally, the subfamily Arecoideae was modified to exclude the tribe Caryoteae and to include the tribe Hyophorbeae. © 2006 The Linnean Society of London, Botanical Journal of the Linnean Society, 2006, 151, 15–38.