[Truncated abstract] In 1994, historian of eighteenth-century French medicine Laurence Brockliss posed the question as to whether consulting by letter was a widespread practice in pre-revolutionary France. This thesis sets out to analyse some 2500 letters between patients, members of their families and their local medical advisers written to expert physicians and surgeons and the responses of these experts. Primary source material has been collected from many libraries and archival deposits, large and small, across France in manuscript and printed formats. Whilst scholars have drawn on epistolary consultations for various purposes, this thesis through its large source base seeks to examine the genre in depth to give a broader picture of medical practice on a day-by-day basis than has been previously explored. The thesis investigates the relationships between the various parties as expressed in their correspondence and how these are linked to perceived and actual authorities. It examines the manner in which patients saw their bodies in health and in sickness. It compares the physicians' views of these matters to the changing medical theories of the period and whether or not they migrated into the therapeutic advice proffered. Historical studies of epistolary consulting in countries from England, Spain, Switzerland and Italy have been concerned with the output of physicians. A unique feature of this thesis is that it draws also on consultations written by surgeons a hitherto overlooked aspect of this form of providing medical advice.