After making large investments to put in place effective health and nutrition interventions, researchers, program implementers, policy makers, and donors all expect lasting effects. However, it is uncertain whether this is the case, and there is less certainty on how to approach the study of program sustainability. This symposium, "Building Evidence for Sustainability of Food and Nutrition Intervention Programs in Developing Countries," provided not only frameworks for conceptualizing sustainability but concrete evidence about the approaches and methods used as well as lessons on how they do or do not work in particular contexts. We presented the following findings: 1) sustainability of activities and impacts of Title II food aid programs in Bolivia and Kenya, 2) sustainability of impact in terms of adoption and consumption of a biofortified orange sweet potato in Uganda, and 3) lessons from incorporating pro-sustainability investment strategies in child survival programs in Guinea. Our symposium introduced a new important body of research on program sustainability to provide insights and stimulate innovative thinking in the design and planning of further applied research and future prosustainability intervention programs.