The HRL houses microform (predominately microfilm) collections of Slavic, primarily Cyrillic, manuscripts from numerous repositories in dozens of countries. Various other languages, scripts and cultures are also represented, with several hundred Greek manuscripts on microfilm (especially from Hilandar Monastery) representing the second largest group of materials.
Resources in the HRL come from individual collections as well as those from national libraries and archives, monasteries, universities, and other institutions of Slavic scholarship, with thousands of manuscripts and millions of folia available. The provenance is fairly equally divided between South and East Slavic resources. Key collections are those representing approximately 80% of the known extant Slavic manuscript material found in monasteries of Mount Athos, Greece. Microfilm collections of Hilandar Monastery are complete and represent the majority of such material. Also included are portions of the Slavic manuscript collections of Zograf, St. Panteliemon, Iveron and the Great Lavra monasteries.