Cold Acclimation—An Altered Steady State Robert E. Smith, Ph.D., Los Angeles COLD ACCLIMATION is a physiological adjustment to prolonged exposure to cold. In effect it is the sum total of adaptive responses by which the animal is enabled to survive in the cold and maintain its body temperature. The intent of the present paper is to summarize the physical factors and physiological events which appear in the course of the long-term response to cold as seen in certain laboratory animals and to some extent in man. Material for this derives importantly from the Proceedings of the International Symposium on Cold Acclimation held in Buenos Aires during the fall of 19591in which I was privileged to participate. It is hoped that the reader will entertain the concepts presented, without demanding the entire complement of specific documentation. For the most part this is available in a number of recent reviews.