This study examines the effect of maternal personal and domestic hygiene on the incidence of diarrhoea in children aged 6-23 months from rural areas around Teknaf, Bangladesh. The intervention area received augmented water supply through handpumps and health education while the control area received no project inputs. From July 1980 to June 1983, diarrhoea incidence was recorded weekly while mothers' personal and domestic hygiene was observed yearly. Annual incidence of diarrhoea in 314 children from the intervention area and 309 children from the control area was analysed in relation to maternal personal and domestic hygiene, controlling for education and occupation of household head and household size. Results show that, in both areas, use of handpump water for drinking and washing, removal of child's faeces from the yard, and maternal handwashing before handling food and after defaecation of self and child, observed together, decreased yearly diarrhoea incidence in children by more than 40% compared to children living in households where none or only one of these practices was observed.