Aristolochiaceae comprises some 600 species occurring worldwide with concentration in tropical and subtropical regions. The family belongs to a basal angiosperms clade concisting of Piperaceae, Saururaceae, and Lactoridaceae; the latter is either nested in or sister to Aristolochiaceae. Although Aristolochiaceae is generally split into subfamilies Asaroideae and Aristolochioideae, strong disagreement exists in systematic relationships at the generic level. This is particularly true for Pararistolochia and Isotrema, although they can be recognized by several morphological synapomorphies. We present a phylogeny based on trnT-trnF for Aristolochiaceae. The two subfamilies are well supported with Saruma and Asarum being sistergroups. Pararistolochia and Isotrema form well supported monophyletic clades, with Endodeca sensu Huber beeing closlely related to Isotrema. The morphologically unique, monotypic Holostylis nests within the South American species of "Howardia“ sensu Huber. Based on a broad sampling of outgroup taxa (e.g., Saururaceae, Piperaceae, Austrobaileaceae, Amborellaceae) we also allows to look for close relatives of the Aristolochiaceae. Special attention was paid to the problem of an presently unresolved position of Lactoris fernandeziana. The outgroup results of this study show Piperaceae and Saururaceae forming a monophyletic group with Lactoris at its base and confirming this grade being sister to Aristolochiaceae.

Key words: Aristolochiaceae, Lactoris, molecular systematics, Piperales, trnT-trnF