Procoralan (S 16257-2) is a selective inhibitor of the pacemaker If current. It reduces in vitro the spontaneous beating rate of the sinus node by slowing the diastolic depolarization slope of the action potential. It induces in vivo a selective and prolonged reduction in heart rate, both at rest and during exercise. It preserves myocardial contractility, atrioventricular conduction and ventricular repolarization duration. Procoralan has a similar anti-ischaemic activity as a beta-adrenergic blocker but it limits to a greater extent the ischaemic myocardial dysfunction. Procoralan should have major therapeutic benefits in ischaemic heart disease, in particular when associated with heart failure.