ENIn the history of science Jurgis Elisonas is known as a naturalist, teacher, folklorist, museologist, bibliographer of literature on zoology. However, another passion of this respectable person - books and archival documents - has been very little discussed. J. Elisonas's correspondence with K. Jablonskis, Vac. Biržiška and other persons preserved at the manuscript department of the Library of the Lithuanian Academy of Sciences shows how for two decades J. Elisonas was collecting books for the library of Kaunas University and the museum, for Antanas Smetona Institute of Lithuanian Philology and K.Jablonskis's private library. Even during hard times of the war (1941-1943) he was replenishing his private library by ordering books not only from Vilnius antiquarian shops but also from Germany, he was taking care of ownerless private libraries all over Lithuania. Letters and other documents witness that thanks to J. Elisonas collections of manuscripts were enriched by valuable historical documents: archives of the Karpiai family and the priest Julijonas Lindė-Dobilas, case files of Upytė Court. Now theses documents are kept at the manuscript departments of the libraries of Vilnius University and the Lithuanian Academy of Sciences. J. Elisonas's particular love and understanding of books were known and valued by the learned and cultured persons of Lithuania of that time. J. Elisonas perfectly understood the importance of the written heritage to the history of the country, therefore he encouraged other people to collect printings, manuscripts, letters, photographs, reminiscences. He was concerned about everything that was Lithuanian. So we must add one more word to the name of J. Elisonas - that is "bibliophile" - lover of books, collector of rare and valuable publications.