The reentrant circuit of common atrial flutter is known to located in the right atrium between two anatomical barriers. Recent electrophysiologic studies have defined the tricuspid annulus as the anterior barrier, and the terminal crest and its continuation as the eustachian ridge as the posterior barrier. Construction of a bidirectional block to conduction between these two barriers by means of lesions created with radiofrequency current have been shown to be effective in ablating the flutter. We now find that surgical creation of such a block to conduction between the barriers by a simple modification of the atrial incision line is equally effective. In a 6-year-old boy, who was admitted to our hospital for closure of an atrial septal defect and treatment of sustained atrial flutter, the atriotomy was performed perpendicular to the terminal groove and extended towards the tricuspid annulus, placing some crythermal lesions between the end of the incision and the annuals. The special defect was closed using a Dacron patch. The child was free of arrhythmia both during the postoperative stay and over the initial three months of follow-up. We conclude that this simple modification of the atrial incision line provides cure of atrial flutter in children who require atriotomy for repair of congential cardiac anomalies. It may also be beneficial in preventing ‘incisional’ reentrant tachycardia.