Traditional classification of the nematodes, based on morphological-ecological characters was evaluated in the context of molecular analysis of systematic taxons, with special regards to ascarids. Division of superfamily Ascaridoidea into 4 families (Heterocheilidae, Ascarididae, Anisakidae, Raphidascarididae) proposed by Fagerhholm (1991) seems to be proved by the molecular data of Nadler (1992, 1995) and Nadler & Hudspeth (1998).