This volume deals with the development of a major phenomenon of the medieval academic world, the adoption, after initial uncertainties, of the Sentences of the twelfth century Peter Lombard as the standard textbook of medieval theology, and the growth of a huge literature of commentary upon it from the thirteenth century. The first of two projected volumes is a survey of this literature and a series of studies of authors and their commentaries in the principal centres of Paris and Oxford and elsewhere, by modern scholars at the leading edge of current research. This should prove an indispensable resource for the future, bringing together as it does the status quaestionis on this literature.