The only attempt at a systematic analysis and classification of Irish accentual verse -metres available to scholars remains that of Prof. Tadhg 6 Donnchadha ('Tórna') , the most recent editions of whose work are half a century old. The present thesis represents a second attempt at the same task, taking into account the contributions of Irish scholars and editors since 6 Donnchadha's time as well as those of more recent metrical scholarship generally. Following a survey of 6 Donnchadha's work and an assessment of its influence upon later editorial practice, an attempt is made to summarise the various schools of metrical scholarship which have emerged in the context of English poetry, with the aim of discovering what principles, if any, might be useful in the construction of a metrical theory for Irish accentual verse. This examination of foreign metrical models is justified on the grounds of the rhythmical similarity between English and Irish, both of which may be described as strongly 'stress -timed' languages. Linguistic phenomena are, indeed, central to the choice of an appropriate theoretical model, and Ch. 3 is devoted to a phenomenologically -based discussion of the role of rhythm in spoken Irish and its implications for verse -structure. Chapters 4 through 10 represent the central part of the thesis and are given over to a taxonomical survey of Irish verse -types, in which the principal criterion for inclusion in a given category is the number of stressed syllables in a line. Chapter 11 discusses the various stanzaic forms, both simple and complex, used by Irish poets, as well as certain supra -stanzaic organisational devices such as refrains and ceangal ver- ses. In this context also the form known as tri rann agus amhrán, often likened to an Irish sonnet, is examined. The ornamentation of verse is the subject of the following chapter, with emphasis placed as much upon the position and function of ornament within the line /stanza as upon the character and linguistic significance of the types of ornament employed. A final chapter is devoted to discussion of the musical context of verse, with particular attention paid to the ways in which musical metre differs from verse -metre, and the implications of such differences for a system of versification primarily transmitted through a musical medium.