The section dedicated to the books on sciences and techniques includes ten manuscripts representing a choice of these specific books present in Friuli since late Middle Ages to the beginning of the Modern Age. Catalogues and inventories of old Friulian libraries record a wide presence of scientific texts or books on a practical subject; the extant whole volumes or fragments of library codices confirm the widespread circulation of works of this kind. The first group includes two encyclopaedic manuscripts: Thomaso de Cantimpré’s De naturis rerum and Brunetto Latini’s Tresor. Unlike the De naturis rerum, the text by Brunetto is no longer written in Latin, but in vernacular French, which in this case is written next to a translation in vernacular Tuscan: a novelty in the encyclopaedic panorama that was evidently conceived for a larger share of readers with respect to the possible number of learned consumers of the Latin language. The second group of works is dedicated to medical science whose pillars were at that time the medicine authors of the Antiquity, Hippocrates and Galen; Microtegni (or Ars parva) is here presented, a compendium of the main work of the latter which illustrates the principles of medical science. This group also includes the Consilia by Geremia Simeoni who was doctor in Udine around the half of the fifteenth century: De conservanda sanitate dedicated to the Venetian patrician Zaccaria Trevisan the Young, General Governor (‘luogotenente’) of the Patria del Friuli in 1452, and Regimen ad pestilentiam, finished at Spilimbergo, where Geremia had found refuge escaping from plague. The third group deals with specific matters, such as Epitoma rei militaris by Vegetius and Mascalcia equorum by Giordano Ruffo di Calabria in two vernacular French translations, Flos duellatorum by Fiore dei Liberi and De trigono balistario by Giovanni Fontana. The book by the noble marshal of the emperor Frederick II of Swabia on the art of horse breeding, written in Latin after the emperor’s death between 1250 and 1256, is one of the first text of a scientific value in medieval Italy; Flos duellatorum by the Friulian Fiore dei Liberi is the oldest Italian manual of fencing technique; the genial work by Giovanni Fontana, of an extraordinary precision, foreruns the scientific texts of the Italian Renaissance.