The present dissertation under the title «Contribution to the study of Nicephorus Gregoras’Letters» aims at analyzing the correspondence of a prominent scholar and scientist of thePalaeologean period. Nicephorus Gregoras, a charming and controversial person,corresponded with lots of literati, church dignitaries and state officials. Throughout thiscorrespondence, which incorporates 159 letters (according to the latest Leone’ s edition) , thereader can trace valuable historical evidence of the first half of 14th century, as well assignificant indications for the education and the sciences’ advancement in the same period.Moreover, the reader can discover, besides the rhetorical tradition and the multitude of ancienthistorical and literary exempla, the reasons which forced the philosopher Gregoras to give uphis ideal «vita contemplativa», for the agitation of the «vita activa», e.g. his involvement inthe Hesychastic controversy.Our dissertation consists of four chapters. In the first chapter a detailed biography of the writeris given, based on the epistolographical evidence as well as on his rivals’ accusations.Additionally, the numerous books published by Gregoras are cited, while several letterallusions to his scientifical, rhetorical and theological works are stated. The aim is to highlightthe fact that Gregoras used to share his projects with his addressees and furthermore his letters were often the motivation which formed the so- called «θέατρα σοφών» in Constantinople, aswell as in Thessaloniki.In the second chapter a summary of each letter is stated, emphasizing on the realia, renderedby its text. Except for the 159 letters that Gregoras wrote, we also summarized the 22 letters,in which he was the addressee, supplementing this way a project that Guilland had started, inhis own edition of Gregoras’ letters.In the third chapter we compiled the network of Gregoras’ correspondents. At this point,bibliography concerning these persons was used, but we particularly focused on the certaincircumstances, in which Gregoras started exchanging letters with them. We also tried to dateseveral letters, that provided us sufficient chronological evidence.In the fourth chapter we first traced the numerous epistolography motifs concerning thefriendship, the nature (animal and vegetation world), the sea, the music, the «φθόνος» and therole of «τύχη», which is dominant in his text. In addition, we showed the way Gregoras useshistorical personalities and situations, in order to compare them with some of his belovedaddressees, such as Alexios Philanthropenos, Ioannes Cantacuzenos and TheodorosMetochites. Finally, we summarized our conclusions concerning Gregoras’ favourite writers,e.g. Plato, Aelius Aristides, Aesopus etc.Having studied thoroughly the text of the letters, as well as the books and articles concerningour study, we came into conclusions concerning Gregoras’ relationship to the literati ofConstantinople and Thessaloniki. Furthermore, we traced important evidence about thefoundation of his διδασκαλείον, his students as well as his pedagogic beliefs. Finally, throughthis text, it is obvious that he was a well- educated and strong- minded man, thus he didn thesitate striving for his religious and scientific beliefs, even though it caused him so manyproblems, including his humiliating funeral.