For more than two decades, WHO and UNICEF have recommended a single formulation of oral rehydration salts (ORS) solution based on glucose and three salts. This product has proven safe and highly effective in treating and preventing dehydration from diarrhoea of all causes and in all age groups in worldwide use and has substantially contributed to the saving of lives in developing countries. However, oral rehydration therapy (ORT) using this formulation does not make diarrhoea any less severe or stop it sooner; which is what is required. During the last 16 yr numerous studies were undertaken to develop an improved ORS that could, in addition to being effective therapy to treat and prevent dehydration, reduce severity and duration of diarrhoea. Controlled clinical trials of ORS formulations containing aminoacids showed that, while they were substantially more absorption efficient in cholera, they were no more effective than standard ORS in infants and children with noncholera diarrhoea; none of these formulations are considered a suitable replacement for standard ORS. Rice-based ORS, in a number of studies, was found superior to standard ORS in adults and children with cholera and its use in such patients is recommended. However, the benefit of using rice-based ORS in infants and small children was either small or insignificant compared to standard ORS, when feeding during ORT was actively pursued. Rice-based ORS was also as effective as standard ORS in infants under 6 months of age and in severely malnourished children. Recently, several studies evaluated glucose-based ORS made hypoosmolar by reducing the concentration of glucose and sodium (with glucose concentration of 75-90 and sodium 60-75 mmol/l and osmolarity of 225-250 mosm/l). These hypoosmolar solutions showed clinically significant benefit in reducing the severity of diarrhoea and the need for supplemental i.v. therapy in infants and children. In limited studies, similar results were obtained in adults with cholera; however, marked hyponatraemia was noted in a small proportion of high purging cholera patients. Two multicentric trials of a hypoosmolar solution, one in adults with cholera and one in children with non-cholera diarrhoea, are ongoing; results of these trials should help us decide whether such a solution could be a practical replacement for standard ORS.