If the late medieval liturgy could be characterized by anything, it was diversity of practice from one place of worship to another, not only in the texts and music used in the services, but also in other areas, including the observance of saints’ days and of special practices with local traditions as well as in the patterns of ritual action that accompanied them. Each pattern of text, music, and ritual is most frequently called a liturgical “use” (from Lat. usus, i.e., “custom”). In medieval England, the most famous of these uses were “Sarum” or Salisbury Use, so called from its emanation from Salisbury Cathedral, and the Use of York, which derived from the practices of York Minster. Both came to be used, on an increasing basis, in their local area and were then adopted on a large scale in the southern and northern ecclesiastical provinces, respectively. These so-called secular Uses (as distinct from the liturgical patterns of monastic or conventual institutions) all stood within the Latin Rite, but they could be distinguished from one another by particular details of ritual and, more noticeably in their written witnesses, by the choice and order of the texts and chants of the Mass and Divine Office. By the turn of the 16th century, the uses of Sarum and York held a near monopoly on the secular English liturgy; by contrast, nearly every diocese on the Continent had its own Use, while other institutions adopted the Use of the Roman Curia. This article includes some of the historical scholarly efforts that have laid the groundwork for further research. Some of these are included for historiographical interest, especially to reflect on the long-held belief in the textual and musical fixity of English liturgical books, which has inevitably led to misconceptions about the ways that modern resources can be used. Catalogues and secondary sources tend, for instance, to use unrepresentative modern editions of liturgical texts and music (often really transcriptions of a single source) with the result that a single reading becomes normative. More recent investigations suggest a more complex textual and musical picture than philology can readily reveal. This bibliography is replete with references that seek to explore the variation in written witnesses, and other witnesses to practice, in order to illustrate the diversity of practice in worship and the richness of liturgical influence on the rest of intellectual activity in the Middle Ages.