This booklet, intended primarily for the trainers of middle-level community health workers in underdeveloped countries, is designed to help such workers present the topic of diarrhea treatment and prevention in training courses. Divided into five sections, the booklet gives guidelines on treatment and prevention, with particular emphasis on the use of oral rehydration in children. It describes, in simple terms, the importance of preventing dehydration in a child with diarrhea, and gives instructions for making rehydration solution, using either packets of oral rehydration salts or locally available materials. Easy-to-follow charts summarize the management of diarrhea and indicate the signs and symptoms that the health worker should look for in assessing the patient and determining treatment. The importance of good domestic hygiene and appropriate child-care practices in preventing diarrhea is stressed, and the role of the health worker in educating the community is given particular attention. (KC)