Contains letters to and from Shilling regarding professional society membership and activities, research in the field of hyperbaric medicine, work in progress, appointments, congratulations, job offers, and evaluations of current technologies. Organizations represented include the Submarine Force, United States Atlantic Fleet; Office of the Surgeon General, U.S. Army; U.S. Atomic Energy Commission, Department of the Navy, Office of Naval Research. Also included is correspondence with individuals representing private and university-based medical practices and research. The professional correspondence is alphabetized. Materials range in date from 1943 to 1987.