The study is a cluster-randomized, controlled trial conducted among 100 villages (including approximately 3500 households and 20,000 people) in Puri district, State of Orissa, India. The study aims to assess the impact of the construction and use of latrines in rural settings on diarrhoeal disease, helminth infections and nutritional status. The study will also report on the cost and cost-effectiveness of the intervention and its impact on lost days at school and work as well as on expenditures on drugs and medical treatment. The study will document how the intervention actually impacts exposure to human excreta along principal transmission pathways by evaluating the impact on (i) faecal contamination of drinking water, (ii) the presence of mechanical vectors (flies) in food preparation areas, and (iii) the presence of faeces in and around participating households and villages. The study will also explore the extent to which different levels of acquisition and use of on-site sanitation among householders impact disease throughout the community.