This book represents tangible results of the Institute of Applied Physiology and Medicine's objectives of bringing into clinical application the concepts and results of bioengineers and physiologists. lt has grown out of our experience in development of original Doppler diagnostic instrumentation and its application to more than 6,000 patients in non-invasive diagnosis of the extracranial cerebrovascular circulation. It gath­ ers together bioengineering and physiological concepts which were initially developed for a graduate course for physicians and specialized medical tech­ nicians. lt should be of particular interest to physicians and medical technol­ ogists whose specialties lie in the field of neurology, vascular surgery, and radiology. The particular selection of techniques on our complete cerebrovascular non-invasive evaluation was chosen primarily to provide an integrated approach relying primarily on Doppler ultrasonic audio signals, but in addition utilizing a pertinent history and physical examination of the patient. The examination is performed by a specially trained physiology technician. Suffi­ cient data is provided to the interpreting physician who develops a consulta­ tive report for the referring physician. The ultimate objective is prevention of stroke and symptoms of cerebrovascular insufficiency. The Doppler functional information supplements the angiography anatomical management decisions for angiography and surgery, anti-platelet or anti-coagulant medication, or to follow the patient with no special treatment.