Why write a book on the tourniquet? The tourniquet is used routinely in op- ating theatres throughout the world, but as far as I know there is no single book that surveys the considerable literature that has accumulated. If used sensibly, the tourniquet is a safe instrument. Most of the few complications seen with its use are preventable. However, when something untoward happens, the tour- quet suddenly becomes an interesting subject, particularly if there is the likelihood of medicolegal consequences. This book summarises the scientific background of the tourniquet and describes a safe physiological approach to preventing complications. Examples of medicolegal problems are included. Considerable progress had been made since Lister first excised a tuberculous wrist joint in a bloodless field. Many researchers have studied the effects of ischaemia and pressure on nerves and muscles. Tourniquets have entered the age of computers and are now much more sophisticated. Despite this, there is still much dogma surrounding the tourniquet in operating theatres and in textbooks. This book is aimed at orthopaedic surgeons, anaesthetists and op- ating-theatre staff. I hope that this short text will stimulate a more widespread interest in the tour- quet and improve safe practice.