MANNED SPACE FLIGHT introduces into space travel parameters that are unique. Man can live without food for a reasonably long period; without water, the period becomes quite a bit shorter; but without air, the result-almost instantaneous-is death. This would make the atmosphere the most important consideration. In fact, however, man needs all three components: oxygen, water, and food; and if anyone of them failS, he is doomed. With our space efforts approaching trips of several weeks in length and certainly heading for month-long journeys, it is most appropriate to ask: Are we ready to provide an adequate atmo spheric milieu for the astronauts? The present volume represents the first integrated attempt to answer this question on a scientific level and on a broad basis of physical and mechanical, biological, biochemical and medical factors. The main features of this work were presented at a symposium of the Division of Industrial and Engineering Chemistry of the American Chemical Society, held in Atlantic City on Septem ber 13, 1965. The volume is an expanded and reorganized treatise based on, but not merely proceeding from, the symposium. Obviously, medical aspects are of paramount importance. A down-to-earth appraisal of the status quo, presented by Dr. E. M. Roth, shows that the problem of 100% oxygen atmosphere still is beset with some uncertainty in the 200 to 500 mm. total cabin pressure range. Additionally, attention is called to inherent dangers of greatly increased flammability in such an atmosphere.