There is limited evidence to demonstrate whether or not water quality, sanitation, and handwashing (WASH) interventions can improve measures of environmental enteropathy, child growth and development, and whether nutritional interventions could be enhanced if provided concurrently with WASH interventions. To help fill this evidence gap, the WASH Benefits study will deliver randomized interventions designed to reduce infection and improve nutrition, and will measure intervention effects on child illness, growth and development. WASH Benefits includes two, comparable but standalone trials in Bangladesh and Kenya that are registered under separate protocols.