The majority of British dams are old earth embankments built many years ago without the benefits of modern earthmoving plant or our current understanding of soil behaviour. Some deterioration with time can be expected and the long term performance of these old embankment dams is of considerable significance for reservoir safety. The guide deals primarily with matters which relate to the safety of embankment dams in the United Kingdom. It includes a brief history of the development of embankment dam engineering in Britain and the geotechnical background to dam safety. It also provides information on surveillance and on the identification of defects, deterioration and inadequacies. Investigations, instrumentation, remedial works and emergency actions are described.