This work examines the country house libraries of Great Britain and Northern Ireland. Hitherto this is an area largely overlooked both in terms of librarianship and social history. The first part of the thesis examines the historical development of book collections within country houses. In addition to pure historical bibliography it also examines the two essentials behind their development, the people and the houses. The work goes on to focus on the current situation within the United Kingdom. By means of a near comprehensive survey of extant collections, the current picture is identified in terms of the types of material, the collectors, the condition of material, the methods of preservation and, significantly, the willingness of owners to concede access. All of these issues are fundamental components in the study and have been investigated further in order to enable the attainment of the final objective, the creation of a national heritage policy for these collections. This final element focuses particularly on methods of preservation, the potential for funding and the question of access to collections. The policy relies on evidence acquired at the earlier stages of the research as well as that acquired during a second survey dealing predominantly with preservation, access and funding. This is coupled with the identification of current best practice within the library preservation field. Extensive use has been made of contact with owners and administrators of collections by means of the surveys, interviews, observational visits and correspondence. In addition, heritage organisations and structures within the United Kingdom have been analysed, with emphasis on those with direct impact on the country house. This research is fundamentally about two things: the historical development of collections and the approaches likely to ensure their survival.