This thesis presents a comprehensive linguistic commentary on one of the fundamental liturgical texts in the Orthodox Church, namely the Oktoikh, which was printed at Spiridon Sobol’s press in the first half of the 17th century.Because of time restriction I have chosen to examine only the first two modes of the Oktoikh as well as the Preface comprising two short texts on the nature of prayer. The study consists of six chapters and an appendix that presents a transcription of the examined portions of the text. Every care was taken to render the text accurately and to preserve, as far as possible, its original orthographic conventions. Chapter I provides non-linguistic information pertinent to the Oktoikh. It gives a brief description of the Orthodox service and liturgical texts used in its celebration, the origin and types of oktoikh, as well as a detailed description of the contents and physical characteristics of the Oktoikh. Chapter II focuses on orthography. The first half of the chapter examines orthographic conventions of the Oktoikh, and explores issues such as spacing, punctuation, capitalisation, distribution of allographs, diacritical marks. In the second part, orthography is analysed from the point of view of its phonological significance; in other words, it considers what orthography may reveal about pronunciation. Chapter III gives a comprehensive analysis of nominal, adjectival and pronominal declension systems. This chapter also discusses the use of numerals and adverbs in the Oktoikh. Chapter IV provides a detailed examination of the verbal morphology found in the text. Chapter V gives a short account of syntax in the Oktoikh – the focus here is primarily on syntactical features characteristic of Church Slavonic and those betraying vernacular influence. Chapter VI is a summary of the most important findings and their significance, as well as a conclusion. The Oktoikh was printed little more than a decade later after one of the first comprehensive works on Church Slavonic grammar had been published, namely Smotryc’kyj’s Grammatiki slavenskija pravilnoe sintagma (1619). Comparison is therefore made, where relevant, between features of the text at hand and Smotryc’kyj’s newly codified version of Church Slavonic.