Temperature is one facet in the mosaic of physical and biotic factors that describes the niche of an animal. Ofthe physical factors it is ecologically the most important. for it is a factor that is all-pervasive and one that. in most environments. lacks spatial or temporal constancy. Evolution has produced a wide variety of adaptive strategies and tactics to exploit or deal with this variable environmental factor. The ease with which temperature can be measured. and controlled experimentally. together with its widespread influence on the affairs of animals. has understandably led to a large. dispersed literature. In spite of this no recent book provides a comprehensive treatment of the biology of animals in relation to temperature. Our intention in writing this book was to fill that gap. We hope we have provided a modern statement with a critical synthesis of this diverse field. which will be suitable and stimulating for both advanced undergraduate and post graduate students of biology. This book is emphatically not intended as a monographical review. as thermal biology is such a diverse. developed discipline that it could not be encompassed within the confines of a book of this size.