Parasites that manipulate the behaviour of their hosts represent striking examples of adaptation by natural selection. This field of study is now moving beyond its descriptive phase and into more exciting areas where the processes and patterns of such dramatic adaptations can be better understood. This book provides a review of host manipulation by parasites that assesses the current state of developments in the field and lays out a framework for future research. It also promotes a greater integration of behavioural ecology with studies of host manipulation (behavioural ecology has tended to concentrate mainly on behaviour expressed by free living organisms and is far less focused on the role of parasites in shaping behaviour). To help achieve this, the book adopts the approach of having an expert on behavioural ecology (but who does not work directly on parasites) to provide an afterword to each chapter.