Sustainability is a critical determinant of scale and impact of health sector development assistance programs. Working with USAID/Nepal implementing partners, we adapted a sustainability assessment framework to help USAID test how an evaluation tool could inform its health portfolio management. The essential first process step was to define the boundaries of the local system being examined. This local system-the unit of analysis of the study-was defined as the health district.We developed a standardized set of assessment tools to measure 53 indicators. Data collection was carried out over 4 weeks by a Nepalese agency. Scaling and combining indicators into six component indices provided a map of progress toward sustainable maternal, child, health, and family planning results for the five districts included in this pilot study, ranked from "no sustainability" to "beginning of sustainability."We conclude that systematic application of the Sustainability Framework could improve the health sector investment decisions of development agencies. It could also give districts an information base on which to build autonomy and accountability. The ability to form and test hypotheses about the sustainability of outcomes under various funding strategies-made possible by this approach-will be a prerequisite for more efficiently meeting the global health agenda.