The effects of intravenous doses of Org 6001 and disopyramide (10 mg/kg) known to confer protection against early postligation-induced arrhythmias in the anaesthetized rat when given prophylactically, were assessed following postligation administration. When given 1 min after ligation both drugs greatly reduced the incidence of ventricular fibrilloflutter and completely prevented electrical deaths (45% in the controls). Protection was also seen when the drugs were given just before the expected onset of arrhythmias (4.5 min postligation).