The JCNAS (Joint Committee of the National Amenity Societies) brings together a group of national societies interested in the historic environment of England and Wales. Seven bodies form its core membership: the Ancient Monuments Society, Council for British Archaeology, Garden History Society, Georgian Group, Society for the Protection of Ancient Buildings (SPAB), Twentieth Century Society and Victorian Society. All are national, voluntary sector organisations. These societies are described in planning acts, government circulars and other guidance documents as ‘The National Amenity Societies’. Together these societies represent many thousands of members who care about all aspects of the historic environment. Through this membership of enthusiasts, and the work of the professional staff in individual organisations, the JCNAS exists to promote understanding, appreciation and care of historic buildings, sites and landscapes.

The core membership of the JCNAS works closely with a range of other organisations that share a concern for the historic environment. These include public-sector bodies such as Cadw and Historic England, organisations representing professional memberships such as the Institute for Historic Building Conservation, private owner-organisations such as the Historic Houses Association, as well as voluntary sector bodies with specialist interests such as the Association of Small Historic Towns and Villages (ASHTAV) and Public Monuments and Sculpture Association (PMSA). Links to all JCNAS members and associated organisations can be found in the Heritage Help directory.

The core member-organisations of the JCNAS have a statutory position in the planning process as advisers on certain types of application. Additionally, each organisation is involved with activities such as advice-giving, campaigning, education and training, as well as offering a range of activities and events for members.