This study examines the major health, water, environmental, tourism and other welfare impacts associated with poor sanitation in Cambodia, Indonesia, the Philippines and Vietnam. The impact measurement reported in the study focuses mainly on a narrow definition of sanitation ? human excreta management and related hygiene practices. The measurement of water resource impact also includes grey water, and the measurement of environmental impact includes solid waste management. By examining the economic impacts of poor sanitation, and the potential gains from improved sanitation, this study provides important evidence to support further investment in sanitation.