It has been pointed out that the editing of a scientific treatise should be “an extended and challenging exercise in judgment, requiring an earnest commitment to scholarship” (Keiser 1998: 110). In the present article, the challenges and steps involved in the process of editing a specific Middle English medical text, G.U.L. MS Hunter 509, are dealt with. After a brief introduction to the manuscript, the stages previous to editing are discussed. These include transcription, of which the main difficulties are addressed and possible ways to overcome them put forward, lemmatisation and morphological tagging. Then, the two types of edition that have been carried out, printed and electronic, are presented. A comment on the glossary and list of lemmas closes the article.