The use of external electrical countershock in the treatment of ventricular and supraventricular tachycardia inadultshas been the subject of several recent reports.1-5Paul and Miller6used external electrical countershock to terminate persistent supraventricular arrhythmias, resistant to drug therapy, in three children (ages 9 to 15 years) with congenital heart disease. The purpose of this communication is to report the successful use of external electrical countershock in terminating persistent rapid atrial tachycardia in a 7-month-oldinfantwith an otherwise normal cardiovascular system. It is not the purpose of this report to discuss the semantics of whether this infant had atrial tachycardia or atrial Report of a Case A 7-month-old, white, male infant was admitted to the University of Colorado Medical Center on Nov 12, 1963. History revealed that the baby was the product of a normal pregnancy and delivery with a birth weight of 9 lb l5]/2