The study of Latin manuscripts has been of vital importance not only to the student of classical and patristic literature but also to every serious scholar interested in the literature, theology, philosophy and science of the Middle Ages and of the Renaissance. In this field, the manuscripts contain not merely new variants of well-known texts but an often unsuspected amount of new textual material that never got into print but often had as wide a circulation and importance as some of the printed works. This material is by no means easily accessible. If a collection of manuscripts has no printed catalogue, there is no way of investigating its content except by working on the spot. On the other hand, printed catalogues, when available, permit the location of pertinent material from a distance, and hence are a definite scholarly aid and desideratum. Since even the printed catalogues are often inadequate and sometimes rare, it has seemed useful to compile an annotated bibliography of these catalogues, which would serve as a guide to medievalists and Renaissance scholars in general, and in particular to the contributors to the project of ‘Medieval and Renaissance Latin Translations and Commentaries,’ which has been undertaken by a group of scholars under the auspices of several learned societies. The present bibliography was originally compiled for the purposes of that project, and it has been decided to print it, since previous bibliographies of a similar nature were either conceived along narrower lines, like Weinberger's, or were inaccurate, like Richardson's.