Discovery of intestinal sodium-glucose transport was the basis for development of oral rehydration solution, and was hailed as potentially the most important medical advance of the 20th century. Before widespread use of oral rehydration solution, treatment for diarrhoea was restricted to intravenous fluid replacement, for which patients had to go to a health-care facility to access appropriate equipment. These facilities were usually neither available nor reasonable to use in the resource-poor settings most affected by diarrhoea. Use of oral rehydration solution has stagnated, despite being effective, inexpensive, and widely available. Thus, diarrhoea continues to be a leading cause of child death with consistent mortality rates during the past 5 years.