The present paper reveals the significance of the National Archival Fund for preservation of the historical and cultural memory of the Bulgarian nation and the formation of historical consciousness. The National Archives Fund is defined as the largest collection of documents with historical, scientific, social, economic, cultural significance as an essential part of the cultural and historical heritage of Bulgaria.It treasures documents about the history of thousands of institutions and prominent figures of the state, economy, culture and art, of ordinary citizens whose activity is historically important in one respect or another.The emphasis of the study is on the main factors determining the daily enrichment of the National Archival Fund with new documents. Among these key factors are development of documentaristics and archivistics, trends in social development, ideological and political climate, financial stability and attitude of the society as a whole, of the istitutional leaders and administrative heads, creating documents, in particular, of the non-governmental organizations and even of the individual citizen to the problems in the field of archivistics.In the focus of the paper as well is the leading role of the state archives for the formation of the National Archival Fund of Bulgaria and the opportunities for cooperation with museums, libraries, community centers and other institutions of memory working with the same purpose and vision.