As can be expected in an ecologically defined group of organisms, carnivorous plants (unlike orchids or cacti) do not constitute one single natural taxonomic unit marked by common descent and close interrelationship. On the contrary, several lines (derived from four different orders of flowering plants) have given rise to carnivorous families or genera (see Figure 1). The classification of at least some carnivorous families is not settled yet, so a somewhat extended discussion of different lines of evidence shall be presented here.