Two patients with intractable life-threatening ventricular tachycardias have been studied using intracardiac electrograms and programmed electrical stimulation of the heart. Both patients have shown to have an underlying re-entry mechanism in the ventricles as the basis for the tachycardias. Both patients underwent epicardial mapping studies at cardiac surgery, and the site of re-entry was established. In one patient the re-entry front was found to start in the posterobasal region of the left ventricle and in the other patient the re-entry front was found in the anterobasal region of the right ventricle. In both patients surgical interruption of the re-entry front was carried out. Both patients are alive and free from tachycardias at the time of writing.