There have been numerous changes in botanical names of New Zealand weeds and their assignment to plant families since the publication of the relevant Flora of New Zealand volumes. This paper outlines the reasons behind the changes in nomenclature, including the recent use of DNA sequencing to classify plants by the Angiosperm Phylogeny Group (APG). Currently accepted name changes and new ... [Show full abstract] assignment of families for weeds in New Zealand are listed. INTRODUCTION The standard references for the introduced plants in New Zealand are three volumes of the Flora of New Zealand series. Volume 3 covered all naturalised monocotyledonous plants with the exception of grasses (Healy & Edgar 1980); Volume 4 covered naturalised pteridophytes, gymnosperms and dicotyledonous plants (Webb et al. 1988) and, most recently, in Volume 5 Edgar & Connor (2000) have covered grasses, both native and naturalised. Since these volumes were published, taxonomists, both in New Zealand and overseas, have continued to increase knowledge of the world's flora. This paper presents the currently accepted botanical names of introduced weeds in New Zealand and also notes changes to their plant families where these differ from the Flora treatments. These new names and family arrangements are used in the most recent edition of "An Illustrated Guide to Common Weeds of New Zealand" (Popay et al. 2010). The new names are also followed in the Landcare Research Nga Tipu o Aotearoa – New Zealand Plants databases (Landcare Research 2010).