This is a translation and update of Lorenzen's original German 1981 review on the systematics of free living nematodes. A phylogenetic assessment of known and new characters is given followed by an outline of a phylogenetic system for the free living nematode orders Chromadoria, Monhysterida and Enoplida and genera incertae sedis of the free living Adenophorea (except the Dorylaimida). Remarks on the gross systematic classification of the free living Secernentea (Rhabditida and Tylenchida) are provided.