This book presents for the first time an in-depth historical account of vowel prosthesis in the Romance languages. Vowel prosthesis is a change which involves the appearance of a non-etymological vowel at the beginning of a word: a familiar example is the initial e which appears in the development of Latin sperare to Spanish esperar and French espérer ‘to hope’. Despite its widespread incidence in the Romance languages, it has remained poorly studied. In his wide-ranging comparative coverage, Professor Sampson identifies three main categories of vowel prosthesis that have occurred and explores in detail their historical trajectory and the relationship between them. The presentation draws freely throughout on the rich philological materials available from Romance and brings to light various unexpected changes in the productive use of prosthesis through time. For example in French and Italian (which is Tuscan-based), one category of prosthesis became well established in the early Middle Ages only to lose productivity and subsequently become moribund. With its extensive use of empirical data and findings from theoretical linguistics, the book offers a thorough and revealing account of a fascinating chapter in the phonological history of Romance.