Worcester Cathedral Library contains 277 medieval manuscripts, the largest number of any English cathedral except Durham. Most of them belonged to the pre-Reformation Cathedral Priory and date between the eleventh and late fifteenth centuries. The collection has never been adequately catalogued before, and is consequently little known; much of the contents of the books, their physical features and history, is here described for the first time. The library is rich in late medieval theology and sermon-literature. Many of the books are important because of their connections with Oxford University, and constitute a valuable source for the history of studies there after c.1300. The Worcester monks tended to annotate and write their names in their books, and some seventy of them are identified. Great treasures are the Worcester Antiphoner, and the fragments of early polyphonic music, some newly-discovered and described for the first time. About half the books are in their medieval bindings, including the second-oldest intact Anglo-Saxon binding. These are described individually, and the history of binding at the Cathedral Priory traced, by Michael Gullick.The rest of the Introduction is devoted to the history of the books and library to the early 1600s. There are indexes of incipits and of manuscripts other than those catalogued, as well as a general index. R.M. Thomson is Emeritus Professor of History, University of Tasmania. Thsi work includes Michael Gullick, other cathedral library catalogues; catalogue of the manuscripts of Hereford Cathedral Library and catalogue of the manuscripts of Lincoln Cathedral Chapter Library.