This catalog presents for the first time an up-to-date compilation of all library abbreviations as cited in the RISM volumes of series A1, A2, B and C published to date. This catalog also lists abbreviations which are no longer in use, with references tothe currently used abbreviations. In addition, the abbreviations are included from the two leading music encyclopedias "MGG" and "New Groves", which are not (yet) used in RISM volumes. The catalog is an indispensable aid when working with RISM.