Digeneans are among the most common and abundant parasitic worms, second only to nematodes. They are parasites of all classes of vertebrates and many of them have great public health and veterinary significance. Human infections with digeneans are still persistently endemic in many parts of the world. In addition, some species are considered nowadays as emerging or re-emerging parasites. This book gives an up to date comprehensive overview of digeneans of medical importance and those rarely reported as human pathogens. I have tried to set down what is known about this group of parasites in a way that conveys the excitement of the science.