PIP: This article reviews current knowledge on oral rehydration therapy (ORT) for diarrhea in children. The World Health Organization (WHO) has formulated an ORT solution suitable for most cases of diarrhea, regardless of etiology or patient's age. At least 65 separate studies in 21 countries have documented successful use of ORT (largely the WHO formulation). Although it is popularly believed that food intake should be minimized during diarrhea to rest the bowel, fasting impairs the absorption of glucose, salt, water, amino acids, and the activity of disaccharidases. However, even children with intractable diarrhea gain weight and have less diarrhea on diets that are predigested but not hypertonic. Locally available food, such as rice and rice water, and breast milk can be tolerated by children with diarrhea. ORT can play a positive role in reducing anorexia and promoting food intake by restoring appetite. ORT must be delivered through a community-based distribution program to reach the majority of people in developing countries. The minimum elements for such a program are the chemicals, a means to measure them, a container, a source of potable water, education of deliverers and family, and managerial surveillance. Medical backup for ORT failures and evaluation of outcomes are also desirable features. Although ORT packets can be produced for US8 cents, they are not always available to remote areas, leading some to advocate use of table salt and household sugar solutions. The problems of delivery of ORT to those most in need mirror more general problems in health care delivery in developing countries. Nonetheless, in comparison with many curative and preventive health care measures, ORT has an exceptionally high cost-benefit ratio.