This thesis is an edition of the English texts in British Library MS Sloane 3285, an important fifteenth century medical collection, hitherto unpublished. After an introductory preface, the thesis consists of five chapters, followed by the text, notes and a glossary. Non English items are presented in appendices. Chapter 1 offers a description of the book’s make-up, and gives an account of its place within the Sloane collection. This chapter includes a paleographical discussion of various hands in the manuscript. Chapter 2 discusses the language of the different hands. Chapter 3 places the contents of texts in relation to medieval medical practice and theory. This chapter also offers an outline of the various traditions that lie behind these texts. Chapter 4 discusses the medieval provenance of the manuscript and relates it to its intellectual milieu. Chapter 5 outlines the editorial practice of the edition. An edition of the texts then follows, edited on conservative principles as outlined in chapter 5. The intention of this thesis is to reconstruct the mental landscape that informed the creation of this remarkable medieval artefact.