The article analyzes the linguistic aspect of Volodymyr Peretz's researches based on the observations of Stanislav Rosovetskyi. Emphasis is placed on his conclusion about the existence of a solid baggage of in-depth studies of ancient Ukrainian poetry, polemical literature, and Ukrainian folklore even before V. Peretz's arrival in Kyiv. The urgency of the justification by this energetic organizer of Ukrainian science in 1906 in the local press of the importance of establishing departments of Ukrainian studies at the university: language, literature, history, ethnography and customary law is emphasized. S. Rosovetskyi's linguistic observations on V. Peretz's detailed review of the 1928 edition of Kateryna Hrushevska's Dumas are considered. Emphasis is placed on clarifying the position of P. Zhitetskyi and V. Perets regarding the problem of the origin of opinions. The selection of Church Slavonic elements that are not inherent in the living prose and song language by V. Peretz in P. Zhitetskyi's language of Dum is highlighted. Also, S. Rosovetsky emphasized the academician's identification of falsifications among the given corpus of authentic texts of opinions. Attention is focused on the experience of Stanislav Kazimirovych regarding the study of forgeries of oral poetic texts: their differentiation into "fakelore", "folklorism", "folksiness", and attempts to understand certain linguistic aspects of their functioning in Ukraine. In addition, he noted the conclusion of the academician about the impossibility of obtaining reliable results when applying "accurate" research methods as a result of insufficient sample size. The role of V. Peretz in starting the scientific model of Shevchenko studies is outlined, on the one hand in his own studios, and on the other hand, in the training of a galaxy of future Shevchenko scholars at the Seminary. S. Rosovetskiy emphasizes meaning of the "originator of the philological method" right down to the word. Separately, the scientist emphasized the importance for a philologist to work with primary sources and introduce new texts into scientific circulation. Emphasis is placed on the possibilities opened up thanks to the "Slavic formalism" invented by V. Perets in 1905, as proved by S. Rosovetskyi. Particular attention is paid to V. Peretz's thorough observations on "The Tale of Igor's Campaign", the linguistic aspects of the scientist's studies are emphasized.