Atrial tachycardia (AT) and atrial fibrillation (AF) were observed in a 21-year old male who had a history of patch closure for an atrial septal defect (ASD) at the age of 5 and a persistent left superior vena cava (LSVC). During electrophysiologic study, atrial extrastimuli reproducibly induced AT which spontaneously terminated or changed into AF. Electroanatomical mapping revealed focal AT arising from the floor of the proximal LSVC. Radio- frequency applications within LSVC targeted to the earliest activation site of AT as well as the complex fractionated potential eliminated both AT and AF without trans-septal puncture.