1. 1. Results of therapy are summarized in 28 episodes of transient (less than 72 hours' duration) atrial flutter in 24 patients and in 55 episodes of established (more than 72 hours' duration) atrial flutter in 48 patients. 2. 2. Digitalis is the drug of choice in the management of atrial flutter in patients with serious organic heart disease or cardiac decompensation, or where there is a specific contraindication to quinidine. It usually acts by instituting atrial fibrillation, which reverts to sinus rhythm on its withdrawal, particularly if quinidine is then given. Even in the refractory cases, or when permanent atrial fibrillation is established, the slow ventricular rate maintained by digitalis provides for adequate cardiac function. Digitalis may also convert the atrial flutter directly to sinus rhythm, but in some of these cases a temporary period of atrial fibrillation may be missed. 3. 3. With the exception of increased rapidity of digitalization, the pure crystalline oral and intravenous digitalis glycosides showed little advantage over digitalis leaf in this series. However, these preparations were outstanding in certain individual cases and deserve further study. 4. 4. Oral quinidine sulfate alone proved effective in restoring sinus rhythm in selected patients without cardiac decompensation and without grave organic heart disease, particularly if the atrial flutter was of short duration. It has the disadvantage of being a myocardial depressant and on rare occasions initiates 1:1 conduction with the hazards of a rapid ventricular rate. 5. 5. In unusually refractory cases, when previous attempts have been unsuccessful in influencing the circurhythmia, intravenous quinidine lactate or gluconate may be justified in the attempt to institute sinoatrial rhythm, but only with frequent blood pressure determinations and under constant, direct electrocardiographic control. 6. 6. Combinations of quinidine and digitalis concurrently were less effective than either alone or in sequence, but they appear desirable whenever atrial flutter occurs in acute myocardial infarction with cardiac decompensation, and when 1:1 rhythm has once developed with quinidine alone. 7. 7. Maintenance doses of quinidine, potassium, or possibly Cedilanid are variously dependable after reversion in preventing recurrences. 8. 8. Prognosis, in general, depends upon the underlying myocardial condition. It is particularly poor whenever atrial flutter complicates myocardial infarction and when atrial flutter is an episode in terminal states.