This article is reprinted from Fundamentals of Hyperbaric Medicine by permission of the National Academy of Sciences-National Research Council. It serves both as a chapter, under the authorship of Dr. Severinghaus, in the NAS-NRC volume and as the first report to the American Society of Anesthesiologists of the Committee assigned by the Society to investigate all aspects of hyperbaric oxygenation as they affect anesthesiology. This committee of the A.S.A. consists of Drs. A. H. Behnke, E. I. Eger, II, Peter Hall, Louis H. Lambert, Martin L. Norton Robert M. Smith, Carl Wasmuth, Peter Safar and John Severinghaus, Chairman. The committee also used the consultant services of Drs. Harry Churchill-Davidson, Jon Pegg, Sheldon Gottlieb, Heinz Schreiner, Edward Lanphier and Manno Sluijter.