This is an introduction to the study of marine rocky shores in the temperate zone. It is designed to encourage students and others to couple enormous intellectual rewards with the pleasure of working in some of the last easily accessible but relatively unspoilt places, and can be used as a basis for field courses, project work, or for lectures. Centred in North-West Europe, but using examples from all over the world, the book begins by considering the physical factors that characterize the habitat - primarily tides and waves - and goes on to assess how they influence the organisms that live within it. It describes how the behaviour and physiology of individuals belonging to the major groups - algae, grazers, suspension feeders, and predators - are affected by their habitat, how their communities are structured, and discusses theories of community organization. For field courses, it suggests experiments and observations that can be carried out on the shore or in nearby laboratories. Finally, problems of pollution and conservation are considered in the context of their effects upon biodiversity.