This thesis surveys the gradual emergence and development of the English testament from the earliest surviving examples until 1499. The introductory section of this interdisciplinary study examines the religious and legal origins of the first vernacular dispositive acts, the oral roots of the testamentary process in the Anglo-Saxon period, and the development of the written will in the centuries before and after the Conquest, including detailed comparisons between early thirteenth-century texts from Worcester and Exeter. The second section begins by examining the processes of will-writing in later-medieval England in detail, analysing the essential linguistic components of the canonical testament before using two specific groups of wills from mid-fourteenth- and late-fifteenth-century London to explore nuances of composition and phrasing. Having established the context and structure of the developed form, a detailed comparative analysis of the testamentary language contrasts the phrasing of wills written in Latin and French with that used in the emerging English texts. The succeeding chapters focus on the testamentary archives of Bury St Edmunds and York, these case studies including examination of vernacular texts composed on behalf of women, trends in urban and rural usage, the effect of periods of high mortality on language choice, scribal methods, and the regional character of testamentary language