During his university career Professor em. L.M. de Rijk has compiled notes on medieval manuscripts containing logical texts. From 1953 onwards Professor De Rijk has visited a great number of libraries in Europe, he has studied many microfilms, and analysed numerous catalogues. He took down shelfmarks, folionumbers, titles of tracts, author names, names of the author commented on, incipits, explicits, colophon, year or centuries. He recorded these data on a great number of filing cards and made use of them for many of his books and articles. This database is meant as a repertory of medieval Latin texts on logic in medieval manuscripts (medieval in both cases means written between 500 and 1500). The ars vetus and ars nova themselves (including texts with interlinear or marginal glosses and De sex principiis) are left out. The database contains commentaries on the ars vetus and nova, texts belonging to the logica moderna, and other texts on logic, such as tracts De artibus liberalibus or just pages of notes. Logicae modernae are split up into tracts, commentaries on the ars vetus or nova into commentaries on the separate works (but not further into commentaries on book I, book II etc.). If a manuscript dates from after 1500, the texts, medieval though they may be, are not included; but this rule is not applied too strictly, because the manuscript might turn out to be medieval after all. Codicological and paleographical aspects are only noted when relevant for the history of the text (e.g. provenance and colophon are included, but format and material are omitted). In many records, a large part of the fields is still empty; often because the codex simply doesn't contain a colophon, the provenance is unknown and the fields 'umbrella title' and 'author comm.' are not relevant, but just as often because we don't yet have the information. The database is founded on the card files professor De Rijk has been building since the sixties; his interests of course weren't identical with the recent guideline for the database. The data have been supplemented from the available catalogues (it is needless to say that these cover only part of the libraries), but many catalogues give rather scanty information. We shall try to supply at least the most important information (e.g. folio numbers, incipit) from the microfilms available to us. Apart from the fact that many records are incomplete or have not yet been split up, users will also find that the database does not cover all the manuscripts it should cover according to our guideline, because professor De Rijk hasn't perused all the catalogues nor visited all the libraries and we lack the money and time that would be necessary to fill this gap. We can only ask for the users' sympathy for the shortcomings they will find in this database and we shall welcome all help in improving it.