This history of the U. S. Army Medical Department deals with the period when the Medical Department existed only as a wartime expedient and concludes with the passage in April 1818 of the law that finally established the department on a permanent basis. The discipline that government Army surgeons and their patients enabled them to control treatment and record its results with a precision and regularity impossible in civilian medicine. Thus Army surgeons and the Medical Department played a large role in the progress of medical science, a role not always recognized by the profession, by the scholarly community, or by the public at large.This new history of the Army Medical Department tells the beginning of that story. It is a significant and long needed contribution to the study of military medicine.