This publication, jointly prepared by WHO, the United Nations Children’s Fund (UNICEF) and the United States Agency for International Development (USAID), summarizes the current evidence on the benefits of WASH for improving nutrition outcomes and describes how WASH interventions can be integrated into nutrition programmes. It provides practical suggestions, targeted at nutrition programme managers and implementers, on both “what” WASH interventions should be included in nutrition programmes and “how” to include them. It also seeks to help the WASH community to better understand their role, both as providers of technical expertise in WASH interventions and in prioritizing longer-term improvements to WASH infrastructure in areas where undernutrition is a concern.