 The effect of large scale handwashing and hygiene promotion campaigns on handwashing behaviour, diarrhoea and respiratory infections is not known. While Intensive small scale interventions have achieved improvements in handwashing behaviour and reductions in diarrhoea and respiratory infections, it is not clear whether realistic and scalable interventions delivered across large areas achieve effects large enough to be of public health interest. The Unilever School of 5 Lifebuoy campaign is such a scalable intervention that is being rolled out across the state of Bihar during 2015 to 2017. The proposed study aims at evaluation the effect of this campaign on handwashing behaviour in school aged children and their mothers, and on diarrhoea and respiratory infections in the same children and their younger siblings. 