As man projects himself into the strange environment of the universe beyond the life-supporting atmosphere of his native planet, he will encounter physical and psychological forces alien to his experience. The success of his personal conquest of these extra-terrestrial regions will depend in large measure upon his ability to identify these hazards and to neutralize them with protective devices. Space biology, in this pioneer generation of man's exploration of the limitless vertical frontier, is generally confined in definition to the study of these human factors of space flight. This limited use of the term is incorporated into the title and content of this volume. This is not a textbook of space biology, in the sense of offering only a description of present knowledge concerning the physiological aspects of manned space flight. Instead it is an historical survey of research accomplishments from the earliest times which have led to our present state of sophistication in this revolutionary field. In addition to presenting the highlights of our present understanding of space-flight problems, ranging from waste disposal to weightlessness, it seeks to offer some indication of the steps by which we have reached our current level of accomplishment. More than this, it attempts to identify the individual scientists, both in the United States and abroad, who have made important contributions to this progress. - Foreword.