This text, in three volumes, presents a detailed revision of the systematics and taxonomy of the platyhelminth class Trematoda, subclasses Aspidogastrea and Digenea, with key for the identification of these parasites at the superfamily, family, subfamily and generic levels. The trematodes are parasitic worms infecting all vertebrate groups ad include families of significance to human and animal health, with considerable economic impact. The first volume covers the subclass Aspidogastrea and order Stregeida, while the second and third volume cover the orders Echinostomida and Plagiorchiida.