Comprehensive itemisation and technical description of the medieval manuscripts in Pepys's Library. No fewer than twenty-three of Pepys's thirty-eight medieval manuscripts contain Middle English texts, and date from the 14th and 15th centuries. Devotional tracts and religious poetry predominate, though there is also a corpus ofsecular poetry by Lydgate and Chaucer, and some scientific and medical material; a notable rarity is the Caxton Ovid. His Latin books include Bacon's Perspectivaand other treatises on optics, and the mathematical treatisesof Johannes de Nemore. Some books he chose purely for their illustrations, such as a French and Latin Apocalypse and a model book of the 15th century. The oldest book in the collection is a late 12th-century copy of Isidore of Seville's Etymologiae. The catalogue effectively revises, expands, and replaces the 1922 catalogue of M.R. James.ROSAMOND McKITTERICK is Reader in early medieval European history in the University of Cambridge; RICHARD BEADLEis lecturer in English at the University of Cambridge.