Poor initial planning processes have been implicated in the high failure rate of rural water and sanitation development projects. This research explored the relationship between local-level planning processes and long-term project sustainability from an implementer's perspective, through interviews with 30 water and sanitation development professionals from a range of regions and organizational types. Despite agreement among informants that the issues are social and institutional rather than technical, poor technology choice was the most commonly mentioned reason for failed projects. Sensitization of stakeholders to sustainability criteria by which technology can be matched to its intended social and institutional context appears fundamental to increased success. Other proposed improvements to planning include a more intensive phase of acquiring contextual data and understanding, an emphasis on human relationships for the project and the selection of individuals with passion, commitment, and integrity, and explicit calculation of the economic implications of operation and maintenance.