In 1971, the Utrecht University Library purchased an extensive collection of books and journals from various Catholic libraries. The acquisition included around 150,000 volumes from the former Dutch Order of Friars Minor (Franciscan) research-monasteries in Alverna, Weert and Venray. An additional 50,000 items were acquired from Rijsenburg and Dijnselburg, the former training institutes of the archbishopric of Utrecht.
In total, this represents around 6,5 kilometres worth of books, with thousands of volumes being added later, mainly from smaller Franciscan collections and legacies, such as from the Megen monastery. Especially with regard the Franciscans, this collection is unique in the Netherlands.
The collection as a whole is entitled the Thomaasse Collection after the priest Otho Thomaasse (1917-1970), who played a key role in founding the Catholic University of Utrecht (Katholieke Theologische Hogeschool Utrecht (KTHU)). When the KTHU priestly training programme became affiliated with Utrecht University, the decision was taken to house the Catholic study libraries in the Utrecht University Library.
In 1992, the Utrecht University Library published the book Bibliotheken van het aartsbisdom en van de franciscanen [Libraries of the archbishopric and the Franciscans] on the history of the collection.
Most of the volumes in the collection originate from Franciscan collections. It includes 25,000 works printed before 1801, of which 128 are incunables printed before 1501. Of several of the early editions there are no known copies anywhere else in the Netherlands. There is also a small collection of manuscripts.
Including all major works, the Thomaasse collection is the authoritative collection of Franciscan literature in the Netherlands.