BACKGROUND Antiarrhythmic drug refractory recurrent atrial flutter occurred in a 39-year-old man who had undergone successful orthotopic heart transplantation 3 months ago. RESULTS At electrophysiologic study, the transplanted right atrium showed type I atrial flutter. The recipient right atrium was in sinus rhythm with complete atrioatrial dissociation of electrical activity. Mapping demonstrated double-spike electrograms in the low posterior region of the donor right atrium. During radiofrequency current application near this site, the double potentials were dissociated progressively and atrial flutter was terminated immediately. Thereafter, both the recipient and the transplanted atria were in sinus rhythm of different cycle lengths with continued electrical dissociation. CONCLUSIONS This is the first report of successful radiofrequency catheter ablation of atrial flutter in a transplanted heart. Although mapping of the arrhythmia is more difficult due to the large circumference of the right atrium, which consists of parts of the recipient right atrium and the transplanted atrium, ablation should be considered in those patients with drug refractory supraventricular tachyarrhythmias.