Partial left atrial isolation was performed in a 16-year-old girl with persistent atrial tachycardia refractory to antiarrhythmic agents for 3 years. Intraoperative atrial epicardial and endocardial mapping showed that the earliest atrial activation occurred in an area lateral to the junction of the right superior pulmonary vein and the left atrium. An incision isolating the right half of the left atrial body containing the area of the earliest atrial activation and both right pulmonary veins from the remainder of the left atrium was made. The incision was then reapproximated. An excision encircling the interatrial septum containing the upper anterior portion of the septum with early activation was also made, and the atrial septal defect was repaired with a pericardial patch. The patient has been in sinus rhythm and free of arrhythmia for a follow-up period of 12 months.