This paper synthesizes the results of some 25 molecular systematic investigations carried out by numerous researchers over the past six years as they pertain to elucidating the higher level relationships within Apiaceae (Umbelliferae) subfamily Apioideae. Here a variety of molecular characters has been considered, including the comparative sequencing of chloroplast genes (rbcL and matK) and introns (rpl16, rpoC1, and rps16) and the nuclear ribosomal DNA ITS region. Restriction site mapping of the chloroplast genome has also been performed, with these data revealing unprecedented variation in size and position of the inverted repeat. On the basis of these phylogenetic studies and consistent with all available molecular evidence, ten major lineages within the subfamily are erected or confirmed as monophyletic. These are referred to as tribes Aciphylleae, Bupleureae, Careae, Echinophoreae, Heteromorpheae, Oenantheae, Pleurospermeae, Pyramidoptereae, Scandiceae, and Smyrnieae. Tribe Scandiceae includes subtribes Daucinae, Scandicinae, and Torilidinae. Caucalideae sensu Heywood is not monophyletic, containing elements of subtribes Daucinae and Torilidinae. Seven additional groups, such as the Angelica, Apium, Arracacia, Heracleum, and Pimpinella clades, and the apioid superclade, are also recognized but have yet to be treated formally. Relationships among the major clades comprising the apioid superclade are equivocal; moreover, within this superclade several genera are of uncertain phylogenetic placement. Tribe Heteromorpheae is sister to all other apioid taxa investigated, with Bupleureae, Pleurospermeae, the Komarovia clade, and Oenantheae comprising successively more distantly branching lineages. Apioideae, upon the inclusion of the saniculoid genus Lagoecia and the exclusion of the subsaharan African endemic genera Polemanniopsis and Steganotaenia, are monophyletic and sister to subfamily Saniculoideae. Subfamily Hydrocotyloideae, however, are polyphyletic, with the Azorella clade (Azorella, Bolax, and Eremocharis, and possibly Bowlesia and Klotzschia) sister to Apioideae plus Saniculoideae. These molecular data provide the framework from which future revisionary and evolutionary studies within subfamily Apioideae can proceed.

Key words: Apiaceae subfamily Apioideae, chloroplast introns, molecular systematics, phylogeny, Umbelliferae