The Bibliotheca of Photius is an important resource for classicists, Byzantinists, and theologians. It gives an account of texts read by Photius in the middle of the ninth century CE, many of which are now lost, so that we have to rely on his summaries. A number of these include comment on the author's style; Photius was well on the way to inventing what we call the book review. Despite its importance, the accuracy of the transmitted text has not hitherto been scrutinised with sufficient care. For the Oxford Classical Texts edition, to be presented in three volumes, N. G. Wilson has incorporated emendations of some 300 passages, and offered tentative suggestions for the improvement of a similar number. This volume covers the first 221 codices, with a detailed critical apparatus and apparatus testium.