Over the past two centuries, large, important collections of Hebrew manuscripts have been dispersed. Formerly private collections are now in public libraries; individual manuscripts and collections have changed hands; call-numbers have been altered; and, for some manuscripts, researchers have coined arbitrary numbers or used abridged signatures and cognomens. The first edition of Richler's Guide, published in 1994, answered the need for a systematic accounting of these wanderings, providing the reader with basic bibliographical information on the manuscripts cited in scholarly literature and with an important tool for locating them. Since then, new catalogues of important collections have been published, hundreds of manuscripts have changed ownership as private and public collections have been sold, and previously unknown manuscripts have been discovered. Thousands of manuscripts from Eastern Europe recently made accessible to researchers have now been catalogued, enabling the identification of manuscripts hitherto considered lost. Advances in technology have made it possible to trace the present locations of additional 'lost' manuscripts: The now-computerized catalogues of the Institute of Microfilmed Hebrew Manuscripts and other libraries enable complex searches, while the plethora of resources on the Internet and the ubiquity of electronic mail have facilitated the search for information. This new edition represents a complete update and expansion of the first edition of the Guide, including the appendixes pinpointing the present locations of thousands of manuscripts and collections. Benjamin Richler is the emeritus director of the Institute of Microfilmed Hebrew Manuscripts (IMHM) in the National Library of Israel (formerly the Jewish National and University Library) in Jerusalem.