In most broadscale studies Piperales are recognised as one of the best supported clades within basal angiosperms. Although small in number of genera, the group displays a surprisingly high morphological diversity, so that a close phylogenetic relationship is not obviously supported. Based on a dense sampling, representing all genera of Saururaceae and Aristolochiaceae, Lactoridaceae as well as a selection of Piperaceae, we present an analysis inferred from different coding and non-coding regions of the chlorplast genome: the two spacers and the intron of the trnT-trnF region, the matK gene and adjacent regions of the trnK intron. The data show a sister group relationship between Saururaceae and Piperaceae, which both appear to be monophyletic. In previous studies the position of Lactoridaceae and the subfamily Asaroideae of the Aristolochiaceae was not clearly resolved. This ambiguity is considered to arise from long branches leading to either Piperaceae as well as to Asaroideae, and will be adressed in detail. Within Aristolochiaceae subfamily Aristolochioideae, a fully resolved and well supported phylogeny could be obtained. The genus Thottea branches first, followed by two clearly monophyletic clades: One comprises the Asian/American species that are often recognised as genus Isotrema, the other the rest of the family comprising of Pararistolochia, a group of woody lianas and geophytes of Central and South American species of Aristolochia, the Mexican genus Einomeia as well as the old world species of Aristolochia sensu stricto. Within Saururaceae two clades are inferred, one consisting of Saururus and Gymnotheca, the other of Houttuynia and Anemposis.

Key words: Aristolochiaceae, matK, Piperaceae, Piperales, Saururaceae, TrnT-trnF