Incessant monomorphic ventricular bigeminy was studied in a young patient with no organic heart disease. The arrhythmia could not be controlled by drug therapy. Spontaneous and artificial variation of the heart rate showed that reentry was the most likely arrhythmogenic mechanism. Peroperative epicardial and transmural mapping revealed an epicardial focal origin which was cryoablated. Reflected reentry occurring in a small area of working myocardial cells appeared to be the most likely explanation for this arrhythmia.