In his dictionary Lexicon Latino-Illyricum, while writing Croatian, as well as Latin words, Pavao Ritter Vitezović (1652–1713) used some signs above the letters. Different Croatian writers mainly used three signs, inherited from Greek grammars: acute, gravis and circumflex. In Croatian tradition, the usage of those three signs can be observed during 250 years, from Kašić’s Institutiones linguae Illyricae (1604) to the half of the 19th century. But each writer did not use those signs in the same meaning. All Latin words (1810) and all Croatian words (9532) in Vitezović’s Lexicon, marked by a certain sign above a certain letter, are treated in this study. It was possible because the dictionary could be searched by a computer. The use of the three signs, viz. their meaning, marked on Croatian, as well as on Latin words, is described in detail. The research is mostly based on the linguistic concept of opposition (Trubetzkoy, Jakobson). All those examples which differ (24 Latin and 143 Croatian words), viz. which are not in accordance with presented description, are particulary explained. It is also explained why it is so.So far, in Croatia, there were only a few articles on signs above the letters, treating Croatian words, and there was none, treating Latin words. Since the use of those signs in Vitezović’s Lexicon is compared with their use in the works of some other Croatian writers, it is established, at the same time, the basis for a complete description of their use in the history of Croatian literature and linguistics (viz. philology).