THE TECHNIQUE of "controlled hypotension," introduced primarily for the prevention of excessive bleeding during surgical operations, has been embraced by an ever-increasing number of anesthetists and surgeons. In most instances, no doubt, the popularity of the technique is based on its inherent value. However, for those who may be attracted to it by reason of its break with traditional concepts or because of the uninhibited enthusiasm of many published reports, it must be emphasized that multiple dangers accompany its use. The proper evaluation of the technique and a true estimate of its position in anesthetic and surgical practice are dependent upon knowledge both of these complications as well as of the beneficial effects possible for the individual patient. In 1946 Gardner1introduced the technique of arteriotomy, whereby blood is withdrawn from the patient preoperatively via the arterial route and then replaced in part orin totoby the same