After atrial fibrillation, atrial flutter is the most important and most common atrial tachyarrhythmia. Although it was first described 80 years ago, techniques for its diagnosis and management have changed little for decades. The diagnosis rested almost entirely with the 12 lead ECG, and treatment options included only the use of a digitalis compound to slow and control the ventricular response rate, and/or the use of either quinidine or procainamide in an attempt to convert the rhythm to sinus rhythm or to prevent recurrence of atrial flutter once sinus rhythm was established. The past 25 years have produced major changes. A series of studies has advanced our understanding of the mechanism(s) of atrial flutter. Old techniques to diagnose atrial flutter have been significantly refined, and new diagnostic techniques have been developed. Beginning with the advent of DC cardioversion in the 1960s, major advances in the treatment of atrial flutter have occurred. β Blockers and calcium channel blockers are now available for use as an adjunct to or in lieu of digitalis treatment to control the ventricular response rate. New antiarrhythmic agents are available for use to suppress atrial flutter or convert it to sinus rhythm. Atrial pacing techniques to interrupt or suppress atrial flutter have evolved. Catheter ablation techniques either to cure atrial flutter or to control the ventricular response rate have been developed, and related surgical treatments are available. Even automatic low energy cardioversion of atrial flutter to sinus rhythm has been developed. Most of the advances in our understanding of atrial flutter have come from our understanding its mechanism. There is a long history, summarised recently,1 of studies in animal models which have contributed to our understanding of atrial flutter. While those studies have been and continue to be most helpful, a series of studies in patients—principally …