Here we report on a study of 181 episodes of spontaneous atrial flutter (AF) (mean atrial cycle length 250 +/- 32 msec) treated by transesophageal atrial pacing (TAP) in 138 patients (92 men and 46 women; mean age 59.5 +/- 12.6 years). TAP was effective in 163 episodes (90%); sinus rhythm resumption was immediate in 36 (19.9%) and followed a short period of atrial fibrillation in 64 (35.3%); in 63 episodes (34.8%) a stable atrial fibrillation was obtained. TAP was unsuccessful in 18 cases (10%). All the patients tolerated the procedure well. A statistical elaboration with the Fisher exact test did not evidence a correlation between efficacy and age, sex, atrial cycle length, or underlying heart disease but showed a significant correlation between efficacy and AF duration of less than 1 day (p less than 0.05) and absence of antiarrhythmic pharmacologic pretreatment (p less than 0.01). These data strongly support the immediate first-choice use of TAP in AF therapy.