CONTROLLED hypotension has been used extensively in this country and abroad as a means of providing a relatively avascular field for surgical procedures. Three general methods of producing hypotension have been used: arteriotomy, total sympathetic blockade by high spinal anesthesia, and ganglionic blockade. Of the three methods the latter is the most physiologically sound and one of the most widely used. Until recently hexamethonium compounds have been generally employed but had the disadvantage of too prolonged vasodilation. Therefore a shorter-acting drug was sought, and recently the experimental and clinical use of a thiophanium derivative * to produce controlled hypotension has been reported.† Our interest in the use of controlled hypotension as an aid to large blood vessel surgery developed as a result of difficulty in the surgical management of two patients with exceptionally large patent ductus. The experience with one of these patients has been previously reported.4 In that instance