THE conversion of cardiac arrhythmias by directcurrent countershock has become widely accepted but has usually required the use of general anesthesia, with its attendant hazards and practical problems. The last 15 patients undergoing cardioversion in our laboratory have been prepared for electric shock with a single intravenous injection of diazepam,§ a potent tranquilizer and muscle relaxant. Method of Cardioversion Premedication consisted of quinidine sulfate, 200 mg. every six hours for 3 or 4 doses. Five to 20 mg. of diazepam (5 mg. per milliliter) was rapidly administered intravenously. After the onset of sleep the countershock was delivered by the standard . . .