This study consists of an impact evaluation (IE) of the Scaling up Handwashing with Soap (HWWS) and Total Sanitation and Sanitation Marketing (TSSM) projects of the Water and Sanitation Program (WSP) of the World Bank. The objective of this study is to estimate the causal impact of the HWWS and TSSM interventions on the health and welfare of the rural poor in six developing countries: Peru, Tanzania, Senegal, Vietnam, Indonesia, and India. The IE will assess the impact of exposure to the HWWS and TSSM promotion on individual-level hygiene and sanitation practices, and on the health and welfare of children 0-5 years old. By introducing exogenous variation in handwashing and sanitation practices (through exposure to the HWWS and TSSM promotion), the IE will also answer a number of important questions related to the effect of the intended behavioral change (handwashing and improved sanitation) on health and welfare, thus providing information on the extent to which these behaviors alter intended development outcomes. This study uses a cluster-randomized experimental design, whereby the geographic units called clusters (e.g. village, commune, ward, depending on administrative structure of country) are randomly assigned to receive certain components of the Handwashing and Sanitation interventions in the case of treatment arms, and no Handwashing or Sanitation intervention in the case of control arms. . The final sample for the evaluation will consist of approximately 14,000 households, randomly selected, with at least one child between 0 and 24 months of age at baseline. Data will be collected from these 14,000 households (approximately 54,781 subjects) through household surveys, anthropometric measurements, blood and stool samples, direct observations of behaviors, and community surveys. The data collected will be analyzed using a differences in differences approach, where possible, and the results will be disseminated to country officials and others stakeholders.