As a mature technology, hydropowerhas by far the largest installed capacity of any renewablesource of electricity generation. In 1998, in the face ofescalating pressure, the World Commission on Dams (WCD) wasestablished by the World Bank and the International Unionfor Conservation of Nature (IUCN) to review the developmenteffectiveness of large dams and establish a comprehensiveset of guidelines for the design, implementation, andoperation of dams and their decommissioning. Following thefinal report of the WCD, the hydropower industry took manysteps to operationalize its key recommendations and toimprove environmental and social management of hydropowerglobally. In an effort to improve its performance andprovide a consistent approach for assessment, the industrypartnered with civil society, policymakers, and financiersaround the principles of sustainable hydropower. The outputof this process is the multi-stakeholder hydropowersustainability assessment protocol (hereafter referred to asthe protocol).The main purpose of this report is to reflecton the applicability of the protocol in developing countrycontexts, based on the available cases, and offer directionon how it can be used to improve the performance ofhydropower projects in World Bank client countries. Thisreport also seeks to clarify the complementarity of theprotocol with respect to World Bank policies and proceduresand provide input as to the World Bank s role in thegovernance of the protocol. The lessons and recommendationspresented in this report are based on a desk review ofprevious protocol assessments; consultation with World Bankstaff; structured interviews with accredited assessors anddevelopers from previous assessments; as well as directobservations during the pilot assessment of the Trung SonHydropower Project in Vietnam.