Strategies in Cold: Natural Torpidity and Thermogenesis is a collection of review papers presented at the Fifth International Symposium on Mammalian Hibernation, held at Jasper Park Lodge, Alberta, Canada on October 3-8, 1977. The book is organized into four sections encompassing 20 chapters that cover the advances made since the 1971 symposium in the areas of molecular, biochemical, and cellular adaptations of natural torpidity and the role of the central nervous system in regulation of natural torpidity. The opening section discusses the possible ways of generating circannual cycle in constant condition and the historical progress in understanding the mechanism of shallow, daily torpor and its distribution in various families predominantly from the marsupial, insectivore, and rodent orders. The application of simple economic models to biological systems to illustrate the principles of torpor in non-mammalian organisms and temperature regulation is also described in this text. Section II examines the central nervous structures involved in thermoregulation in hibernators and compares these data with the results of corresponding experiments in non-hibernators. Topics on the influence of serotonergic pathways in the brain on hypothalamic hormonal factor release and the maintenance and regulation of hibernation through a parasympathetic response are discussed in this section. Section III deals with the cellular and biochemical adaptations in natural torpidity, with an emphasis on the metabolic and endocrine changes in hibernation. Section IV tackles postulated mechanisms for nonshivering thermogenesis and the neurohumoral factors regulating these mechanisms in mammals exposed to short-term as well as to prolonged periods of cold. A discussion on significance and possible central mechanisms of thermoregulatory threshold deviations in the course of thermal adaptation is also provided.