The incidence of diarrhoea has declined over time in Bangladesh but still it persists as a major cause of infant mortality, morbidity and acute child malnutrition. Much of the public policy thinking in the past was guided by public investment in providing improved access to safe water. While this measure has paid off, the paper provides evidence that the relevance of water as a tool for fighting diarrhoea may have changed over time. Its changing role now needs to be seen in the broader context of combined access with other inputs such as improved sanitation. The paper uses the Bangladesh Demographic and Health Survey data and the propensity score matching technique to suggest that only combined access to improved water and sanitation can lead to reduced incidence of diarrhoea among children in contrast to their isolated use. Mere accesses to safe water, or for that matter, access to sanitation do not have any statistically significant impact on the incidence of childhood diarrhoea.