Diarrhoea remains a leading worldwide cause of morbidity and mortality. In developing countries alone, 1.5 billion episodes of diarrhoea occur per year in children under 5 years of age and approximately 4,000,000 of these result in death. Early, appropriate therapy decreases the risk of complications and death due to diarrhoea. Regardless of the causative agent, oral rehydration and nutritional management are the mainstays of good management of infants, children and adults with diarrhoea. Diarrhoeal disease control programmes throughout the developing world have adopted the WHO case management plan as a standard. In this chapter, we review the history, successes and shortcomings of various oral rehydration therapies and recommend a case management approach that is similar to the WHO plan. Although ORT is safe, effective, convenient and economical, this therapy has not been universally implemented in health care settings. The challenge for clinical and public health practitioners in developing and developed countries is to identify and overcome the barriers that exist so that all patients with diarrhoea will have the opportunity to receive optimal care.