Trinity College Library is a major repository of over 240 manuscripts in Irish.
The project's primary target here was MS 1339 (H 2 18), otherwise known as the Book of Leinster, a diplomatic edition of which was published by the School of Celtic Studies 1954-83 (edited by R. I. Best, Osborn Bergin, M. A. O'Brien, and Anne O'Sullivan). The Book of Leinster, properly Leabhar na Nuachongbhála, is an anthology of Irish tradition - prose, verse, and genealogy - the compilation of which spanned the second half of the twelfth century. It takes its name from an ecclesiastical foundation in Co. Laois, that of Oughaval, near Stradbally. Of the number of scribes who worked on it only one is known by name: Aed mac meic Crimthaind.
ISOS also has digitised the complete collection of Irish medical manuscripts in TCD, the catalogue of which is in preparation at the School of Celtic Studies. TCD's holding of twenty-eight such manuscripts accounts for over a quarter of all extant medical manuscripts in Irish.