Chronic diarrhoea and malnutrition in Gambian children is associated with persisting damage to the mucosa of the small intestine. Intestinal permeability tests suggest that mucosal status gradually deteriorates with age throughout the first year of life in tandem with increasingly severe growth faltering. The ability of the dual sugar permeability test to assess intestinal mucosal status frequently in a non-invasive way makes the technique a valuable tool for future studies into the aetiology of this syndrome.