Parasites evolve under selective pressures which are different from those acting on free-living organisms. The aim of this textbook is to present these pressures and to show how they have shaped the ecology of parasites over evolutionary time. Broad theoretical concepts are explained simply and clearly and illustrated throughout with example organisms. The book will be an invaluable text for advanced undergraduate biologists who are studying evolutionary biology, ecology, population biology, parasitology and evoluationary ecology. It will also prove to be a valuable reference to postgraduate students and researchers in the same fields.