The article offers an overview of the contents and chronological and geographical range of the medieval medical manuscripts in the Harleian collection which has recently been the object of a full cataloguing project sponsored by the Wellcome Trust. It also provides information regarding the provenance of the manuscripts highlighting the role played by both medieval English doctors and practitioners and later collectors in the conservation of such manuscripts. Particular relevance to the collecting activity of Samuel Knott (d. 1687), rector of Combe Raleigh in Devon, as the source of no less than twenty among the 153 Harleian medieval medical manuscripts.