Hexafluorenium was used to potentiat succinylcholine in 36 patients undergoing major surgery, mainly abdominal, of from 1/2 to 7 hours duration. Anesthesia consisted of thiopental-nitrous oxide-oxygen-ether or haIothane and ventilation was controlled. In a first group, succinylcholine was administered for intubaticn and repeated intermittently as required with a single dose of hexafluorenium after the intubating dose of succinylcholine had worn off. In a second group, succinylcholine was administered similary but hexafluorenium was also given intermittenly. In a third group, a single initial dose of hexafluorenium was given followed by succinylcholine intermittently. In a fourth group, both drugs were given intermittently throughout, 1) The apnea time of succinylcholine was prolonged about 8times after a single dose of hexafluorenium in the first and third groups but the prolongation was gradually lessened with successive doses of succinylchohne. Rut in second and fourth groups, the apnea times were significantly prolonged following successive dose of both drugs. 2) In third and fourth groups, fasieulation following succinylcholine was not observed and nausea, vomiting and muscle pains were not noted. 3) In recovery room, about 80% of patients could raise their heads by themselves but ether required longer recovery than halthane. 4) No bronchospasm or cardiovascular side effects were noted. It is considered that this drug combinations provides excellent relatation for surgery. The technique with a single dose of hexafluorenium seems particularlly suitable in cases which last from 30 minutes up to 2 or 3 hours and repeated doses of hexafluorenium and succinylchloin are advisable for longer major cases.