Access to improved drinking water is widely advocated as an effective way to reduce diarrhoea-related morbidity and mortality, particularly in poorest areas of the world and in most vulnerable population segments like children. Initial focus on improved water at the source point has been replaced by an emphasis in promoting interventions to increase access to microbiologically improved drinking water at point-of use. A review is made of the available evidence assessing the impact of specific interventions. Pending confirmation by further research, access to microbiologically improved water at the household level may need scaling-up in developing countries. International organisations may have to change the way of tracking progress of the millennium development target for safe water, replacing the current measurement of the types of water quality by the measurement of the microbiological quality of the water that people actually drink. © 2008, Inderscience Publishers.