Documenting one of the most significant collections of its kind in the United States, Rare Polonica is an important guide for scholars, librarians, and bibliophiles to 514 volumes dating from the 15th through the 18th centuries held by The New York Public Library. Materials include books printed in the Polish-Lithuanian Commonwealth; books printed outside of the homelands by Polish printers; titles by ethnic Polish writers, regardless of place of imprint or language of publication; and works by non-Polish writers printed in the Polish language, or on subjects connected with Poland and/or the Rzeczpospolita. Among the works documented are many early 16th-century editions published in the Kraków shops of Jan Haller, Florian Ungler, Marek Szarffenberg, and Hieronim Wietor, as well as seven of the latter's Viennese imprints. The majority of the titles date from the 17th and 18th centuries, in languages including Latin, Polish, French, German, English, Italian, Spanish, Portuguese, Dutch, and Czech. Reflecting the Library's broad acquisitions policy, the collection covers many fields, with holdings of Reformation literature, editions of the Bible in Polish translation, and historical works being of particularly importance. Bibliographic entries have been constructed according to the Polish standard for the description of early imprints, issued in 1994. Indexes provide access by authors and institutions; printers, publishers, and places of publication; and owners and book dealers.