Schistosomiasis is a disease affecting over 200 million people in developing countries. It is caused by worms that need particular species of fresh water snails for completing their life cycle, and developments in Third World countries have spread and increased the severity of the disease. Dr Jordan describes a 15 year study on St Lucia, a mountainous Caribbean Island where isolated valleys provided ideal field laboratories for comparing the effects on transmission, the advantages and disadvantages of intensive snail control, environmental improvement (providing villages with water), and chemotherapy with newly available drugs. The project was staffed by a multidisciplinary team and their intensive programme led to successful control. This book describes the investigation, fully and readably. It will be valuable to all who work in the fields of tropical medicine, parasitology, epidemiology, community and environmental health, and vital to workers on schistosomiasis control in developing countries.