We report the first case of acute right coronary artery occlusion in an adult patient during radiofrequency catheter ablation of typical atrial flutter. ST segment elevation rapidly resolved with antithrombotic therapy. This complication was thought to be due to the short distance between the endocardium and the right coronary artery at the ablation site, the high-wattage output from the radiofrequency generator, and the lack of sufficient cooling effect related to a severe upstream coronary stenosis. In patients with known right coronary artery stenosis who are suffering from typical atrial flutter, evaluation of the significance of the stenosis would be reasonable.