This policy brief provides an overview of relevant biodiversity issues for those carrying out assessments or studies relating to hydropower development in Vietnam. The Brief is volume 3 in the 5-volume information kit – Biodiversity and Development of the Hydropower Sector: Lessons from the Vietnamese Experience. It targets civil society, Government and donors and aims to be an accessible, practical summary of Volume I – which reviews current knowledge on the relationship between hydropower and its effects on biodiversity as distilled from a number of Strategic Environmental Assessments conducted in Vietnam. The Government of Vietnam has embarked on a major expansion of the hydropower sector, which is transforming the aquatic systems of the country. All main river systems are or will be dammed by one or more hydropower projects – each with road access and transmission lines and linked development shaping the terrestrial, aquatic and social environment.