There is a resurgence of interest in hydropower as a result of the need for low carbon economies and growth in energy demand in rapidly developing countries.The rapid pace of hydropower development in some basins, including the Mekong-Lancang, presents a significant challenge to national governments responsible for the management of international river basins which may be already under pressure from competing needs.The Rapid Basin-wide Hydropower Sustainability Assessment Tool, developed by the MRC in partnership with the ADB and WWF, is a simplified yet comprehensive tool to support dialogue, decision making, and monitoring.It is designed for multi-stakeholders (governments, developers, and civil society) to collectively and rapidly assess, inter alia, hydropower projects within a sub-basin, or transboundary issues for basins with existing or potential hydropower.There are 12 topics,ranging from the economic contribution of hydropower (topic 1) and its impact on biodiversity (topic 3) to project sitting, design and operations (topic 5) and sharing benefits and burdens (topic 6), that enable relevant stakeholders to discuss the uncertainties, weaknesses, and knowledge gaps of hydropower project(s) and ways to address them.The presentation will describe the tool and the experiences to date on its deployment in the four Lower Mekong countries who are members of the Mekong River Commission.