Sixty-five mothers from Balai Lua, Central Lombok, Indonesia were given soap and an explanation of the faecal-oral route of diarrhoea transmission. This very simple health message was repeated and reinforced fortnightly when mothers were also asked whether any members of their family had suffered from diarrhoea over the previous 2 weeks. Children of these mothers experienced an 89% reduction in diarrhoea episodes compared to a control period before the intervention.