49 patients with 53 episodes of atrial flutter were treated by rapid atrial pacing. Sinus rhythm was attained in 55%, atrial fibrillation in 26%, type II flutter in 9% of patients. In the other cases, the effect on atrial action was only slight or short-lasting. Among the causes of the unsuccessful outcome of treatment, the authors include--besides insufficient rate and duration of pacing, bad electrode contact in the atrium and insufficient outlet current--specific properties of the type of flutter (impure flutter, type II flutter, type I atrial fibrillation, uncommon flutter) as well as unsuitable indication (mitral defect, thyrotoxicosis).