This history summarizes the Army Air Forces (AAF) medical achievements that led to the creation of the Air Force Medical Service in July 1949. When the United States entered World War II, our nation's small aviation force belonged to the U.S. Army and relied on the Army medical system for support. The rapid expansion of the AAF and the medical challenges of improved aircraft performance soon placed great strain on the ground-oriented Army medical system. By the end of the war, the AAF had successfully acquired its own medical system oriented to the special needs of air warfare. This accomplishment reflected the determined leadership of AAF medical leaders and the dedication of thousands of medical practitioners who volunteered for aviation medical responsibilities that were often undefined or unfamiliar to them. In the face of new challenges, many American medics responded with hard work and intelligence that contributed greatly to Allied air superiority.