The Helminths are triplolastic animals. The Platyhelminthes are flatworm which comprises about 1500 species; either free living or parasitic and possess many reduced features, however, Aschelminthes are more advanced pseudocoelomate, appearance, free living, epizoic or parasitic. Flatworms exhibit diverse characters, it is very difficult to identify and classify them. The exact systematic position of these parasites could be established only after going through detail study of their genital organs as well as vitellaria and the present book will provide a comprehensive and exhaustive data of these characters. The book deals with some vertebrate Helminth Parasites of Jharkhand belonging to Trematoda and Cestoda. The two groups have undergone profound adaptations to suit their parasitic mode of life. These parasitic adaptations are reflected in their morphology as well as physiology. In this book, many trematode parasites are dealt in detail. Their morphological description is very well synchronized with statistical measurement of various organs of the worm which will be very helpful to conclude about its taxonomy and identification. The trematodes are Apharyngostrige inidiana and Cotylophoron indicum from the intestine of Budo bubo and intestine of goat were not reported from this locality of the country. Similarly, many species of termatodes are described which are discovered from the alimentary canal and other associated organs and all description is based on their morphological characters as well as the statistical observation of their internal organs which made it more accurate for their identification. This book will be very helpful to the students of Helminthology who are interested in the research work on the taxonomy of these worms because various keys are cited in the book for the identification of various helminth upto species level. The vivid and well stained photographs with their measurements of vitellaria, reproductive organs, etc., camera lucida diagram, graphs and histograms will be very much helpful for the identification. Some new species of cestoda and termatoda are also discovered and described for further study. The present book will be very good reference book for HELMINTHOLOGY.