This book gives a comprehensive account of the principles and practical methods applicable to transient temperature measurements in engineering and science. Transient temperatures are taken to be in the range from about 200K to 6000K and with timescales from tenths of nanoseconds to tens of seconds. Within these limits is a very large field of combustion and gas dynamics and these are the principle areas which are addressed. Several new experimental and theoretical techniques are introduced and various modes of thermal failure are described. The chapters move from undergraduate material to the latest methods and are designed to be of use to the widest possible range of engineers, scientists, and students working in universities or in chemical or mechanical engineering. Many applications are described.