In 1746, Dr John Buchanan, recently retired as a medical officer in the British Army, produced a manuscript entitled, 'Regimental Practice, or a Short History of Diseases common to His Majesties own Royal Regiment of Horse Guards when abroad (Commonly called the Blews).' Revised in several stages almost until the time of Buchanan's death in 1767, this work was for the most part based on the author's observations while surgeon to a cavalry regiment serving in Flanders 1742-45, during the War of the Austrian Succession. It is a work of immense value to the understanding of eighteenth-century interpretation and treatment of diseases, but as yet has never been published. Presented here is an annotated modern edition of the text, with an introductory section setting the work in the context of Buchanan's life and career, and within the broader framework of eighteenth-century medical practice. Buchanan's practice of medicine generally represented the mainstream of professional practice as regarded both his understanding of disease and his treatment of it. Across the decades of the eighteenth century there were discoveries and fashions that impacted both the theory and the practice of medicine. Various writers of that age, as well as a number of historians since, have conveyed the sense that practice was chaotic. On the contrary, what this book argues is that methods used to treat diseases were fairly standard. Therefore, by reading Buchanan's manuscript one sees not only how he treated more than three dozen diseases, as well as various wounds and injuries, but also how these conditions were often treated in this period.