This advice is for developers, owners, archaeologists and planners working on projects where the intention is to retain and protect archaeological sites beneath or within the development. It can also be read in relation to other land-use or site management work. It has a particular focus on decision-taking on waterlogged archaeological sites. The emphasis throughout is on the benefits gained, both to sustainable development and the archaeological resource from understanding: • the significance and current state of preservation of the archaeological material • the potential development impacts of the proposed scheme • (in relation to sites containing waterlogged archaeological remains) the availability and quality of water necessary to sustain the long-term future of those sites. It also highlights the likely range of information needed to fully assess these issues and the benefits of pre-application discussion and assessment to promote a viable way forward for sustainable development on what can often be complex sites. Whilst particular sections of this document are focused on waterlogged archaeological sites, the core themes within this advice note, of prior preservation and impact assessment are relevant to all sites. Additional methodological detail and technical advice is provided in the appendices.