ENEven before the Lublin Union (1569) between Poland and Lithuania there was an important linguistic controversy among Lithuanian Humanists. In the wider context of a general ‘Latinization’ of the culture of the Grand Duchy of Lithuania, the so-called ‘Latinizers’ (Agrippa, Rotundus, Michalo Lituanus) harked back to a classic language such as Latin, the dignitas of which was considered to be undisputed. The Latin language could compete with other languages of culture used inside the Grand Duchy, primarily with Ruski. According to the Latinizers the identity of Latin and Lithuanian was the principal evidence to support the derivation of the Lithuanians as a people from the Romans. Promoting Latin was equivalent to promoting vulgar Lithuanian from the point of view of the Latinizers. In this paper I discuss the textual aspects of the debate about the literae (Latin vs. Muscovite or Ruthenian) exposed in the works of Michalo Lituanus (Tractatus de moribus Tartarorwn, Lithuanorum et Moschorum, 1615[1550]) and Augustinus Rotundus (Preface to the second Lithuanian Statute, 1576). Possible implications of the dispute for the question of the Ruthenian language are investigated, too. [From the publication]