Part 1 Adaptation to the seasonality of exposure to cold and food scarcity: control of rhythms by environmental cues; neuroendocrine aspects of rhythmicity; seasonal depression vs hibernation - putative seasonal triggers; food availability, starvation and torpor. Part 2 Effects of cold and resistance adaptation to cold: biochemical and biophysical aspects of cold sensitivity; cold sensitivity and cold adaptation at cell and organ level; experimental hypothermia and clinical applications. Part 3 Control of metabolism in hibernation and torpor. Part 4 Cold defences in relation to cold adaptation and torpor: nonshivering thermogenesis and brown adipose tissue; temperature regulation, torpor and sleep. Part 5 Central nervous system, sleep and hibernation: questions and perspectives for future research.