Atrial flutter is a macroreentrant arrhythmia that is associated with cardiovascular and pulmonary disease. In the United States, 200,000 new cases of atrial flutter can be expected to develop every year with a male to female ratio of over 2:1. This arrhythmia is associated with atrial fibrillation in over half the cases. It is also associated with an increased risk of thromboembolic complications, but less than that is seen with atrial fibrillation. The most common form of atrial flutter involves a large reentrant circuit within the right atrium, encircling the tricuspid annulus. Other, less common forms of atrial flutter may involve other anatomic barriers, atriotomy scars, and infarcted areas of the atria. Treatment of atrial flutter often involves electrical cardioversion and/or antiarrhythmic medications. Type I and Type III antiarrhythmic drugs are often used to terminate or prevent recurrent episodes and Type II (beta-blockers) and Type IV (calcium channel blockers) can be used to control the ventricular rate during atrial flutter. However, antiarrhythmic drugs alone control atrial flutter in only 50% to 60% of patients. Since the early 1990s, radiofrequency catheter ablation has been used to interrupt the reentrant circuit and prevent recurrences of atrial flutter. Radiofrequency ablation is acutely successful in over 90% of cases and avoids the long-term toxicity seen with antiarrhythmic drugs. Advanced mapping techniques and newer methods of delivering the radiofrequency lesions are being used to delineate unusual forms of atrial flutter and to minimize fluoroscopic exposure during the procedure.