This is the second of three volumes of "Keys to the Trematoda," a series on the systematics and identification of the Class Trematoda. The book presents the taxa in the Order "Echinostomida" and some of those in the Order "Plagiorchiida," with keys for their identification at the superfamily, family, subfamily and generic levels. The keys are based on critical examination of specimens by subject experts, and generic diagnoses are accompanied by illustrations of important morphological characters. This volume includes seven echinostomidan superfamilies (the echinostomatoids, haploporoids, haplosplanchnoids, heronimoids, microscaphidioids, paramphistomatoids and pronocephaloids) and two plagiorchiidan superfamilies (the allocreadioids and lepocreadioids). The first volume covered the Subclass "Aspidogastrea" and Order "Strigeida," while the third volume, due to be published in early 2006, will cover the remaining members of the Plagiorchiida.