Helminthes constitute of assemblage of course of comparatively simple and varied organization. Helminthes is derived from the Greek word helmins means worms. The term worms is not correct because it is applied to elangated invertebrates without appendages and with bilateral symmetary. In 18th Century all the worm-like animals was very heterogenous group which included a highly diverse assemblage of forms. In the modern classification this group is divided into several independent phyla such as Platyhelminthes, Aschelminthes, Annelida etc. The term helminthes is restricted to a few phyla of invertebrate animals, all of which are superficially worm like but they differ markedly in their morphology, life-history and bionomics. The helminthes are restricted to two phyla of Animal Kingdom namely: o Platyhelminthes or flat-worms. o Aschelminthes or roundworms. The present work in three volumes is designed to present entire vital information on Helminthes. Profusely illustrated in the light of latest researches, this work will prove a dependable reference work for students, teachers and researchers in the discipline.