This project aims to study the role of Giovanni Tortelli (1400c.-1466) and of his most important work (the Orthographia) in the promotion and dissemination of the study of Greek in Italy and in Europe in the fifteenth century. Friend of Lorenzo Valla, who dedicated to him the Elegantiae, Tortelli collaborated with Pope Nicholas V in founding the Vatican Library and supervised the search for Greek manuscripts and the work of many translators hired by the pope. His work, still largely unknown, represents a crucial cross-section of the role played in the dissemination of Greek culture at that time, when the knowledge of the Hellenic language in Italy and in Europe was still the preserve of a few. My research will provide the first systematic study of the Greek sources of his Orthographia, a bulky dictionary of Greek words transposed into Latin, an enciclopedic dictionary to be used for reading and commenting on the classics. In the ms. Vat. Lat. 1478, the manuscript revised by Tortelli himself, it consists in more than 3.000 words and in about 380 ff. (760 pages). This work was widely diffused in Europe. My project will set the Orthographia in its context, and show its role in the new wave of interest in the spread of Greek studies in the West Europe during the fifteenth century; I will also compare the data coming from the Orthographia with those coming from the study of a complete course of Greek held in Veneto region in the XV century and now preserved in two manuscripts at the Bodleian Library, Oxford. My project will result also in a database devoted to Greek grammars, lexica and school books available in Europe between 1396 and 1529, whose metadata will be linked with the Perseus project catalogue of Gregory Crane's group.