The purpose of the Symposium is familiar to all of you, but permit me the privilege of stating it in my own way. It is our task in the two and onehalf days ahead to look critically at an area that is part science, part superstition, and part unknown, with the view of determining how much time, effort, and money should be spent in its study. We must ask now and throughout the proceedings whether cold is an important factor in modifying or altering host-parasite interaction. We have been brought here by a branch of the Armed Forces of the United States because the medical authorities of that branch charged with the responsibilities of safeguarding the health of military and civilian personnel, who are, for the sake of the security of our country, forced to live in hostile environments, need to have an answer. They arelookingtous for help, and if it is within our wisdom to provide, I know we will. There is before us, therefore, a very real and practical problem which is our primary concern; but there is also the challenge of pure science. Medical and biological science from its earliest history has been preoccupied and inquisitive about the role the environment plays in the behavior and response of living organisms. I do not know to what extent the phases of the moon exert an influence at the time of planting or cultivating, or harvesting the yield and value of crops, but I have heard in my youth from many firm and dogmatic assertions by practicing farmers that they do. I also recall with some nostalgia my mother, my great aunts, and indeed, our faithful country doctor warning against wet feet, cold on the back of the neck, night aii; cooling off too fast from a good sweat and the dire consequences (all of an infectious nature) that would otherwise result. I remember with affection my mother's wish to protect me from the hostile BERRY rigors of a winter in the far north of Texas, Each October I went into long white underwear only to emerge in late March or early April when the air warmea to a comparatively safe 80°F to 90°F. Many of these notions are firmly implanted in the minds of millions of people more from reiteration than by demonstration, to borrow a phrase from a friend (Schneider, 1946). But as is often the case, where conviction is firm, there is often more than a superstitious quicksand to give it support. We can now begin by examining some of the bases for this support, and, I hope, finding what there is of merit, v/hat there is that is formless and amorphous, and where, if anywhere, new work is needed to give form to our knowledge. In undertaking the responsibility of organizing this Symposium, it seemed to me that attention should first be directed to an analysis of past experience of Armed Forces in an arctic environment. During World War II and certainly in Korea, large bodies of men were forced to live and fight at cruelly low temperatures. This was particularly true on the Russian front (for which no direct knowledge is readily accessible), but knowledge is available to an adequate degree around th...