The old prints of the State Archive Library in Olsztyn have not yet been studied. They came into the library between 1947 and 1951 during the securing of archive and library collections from East Prussia. As many as 783 volumes were recognised in terms of provenance structure. The article describes fragments of historic Warmian book collections of Library of the Hosianum High School, heir to the library of the Jesuit College in Braniewo, as well as the Library of St Anna Benefice in Pieniężno. Prints from manorial libraries of the Dohns in Markowo and the Finckensteins in Jaśkowo were characterised. The book collections evacuated by the German authorities from Königsberg and deposited in the estates of East Prussian families with the intention of being exported to the Reich are represented by the stock of the Königsberg Municipal Library. The article points out the need for detailed research, which will be made possible by the Electronic Provenance Database being created by the Library staff as part of the project ‘Pre-War Book Collections as a Source for the History of Warmia and Mazury’.