The first clinical experience and the potential benefit of intraoperative global atrial-activation mapping recorded from 156 electrodes simultaneously are demonstrated in a 14-year-old girl with an ectopic (automatic) right atrial tachycardia, junctional tachycardia, and atrial flutter secondary to a previous atriotomy. Cryoablation of the right atrial focus terminated the automatic tachycardia, and surgical interruption of the atrial flutter pathway temporarily terminated this arrhythmia. Persistence of the junctional tachycardia necessitated elective cryoablation of the bundle of His.