The effectiveness of the "diving reflex" in treating paroxysmal supraventricular tachycardia (PSVT) in 10 infants aged under 6 months is demonstrated. No rhythm disturbances were encountered during the maneuver, even in patients receiving digitalis. The recommended water temperature is 5 degrees C and the total time of facial immersion, between 6 and 7 seconds. The diving reflex might be considered the first therapeutic approach in infants under 6 months old with PSVT.