The electrophysiological properties of of 0,6 mg/Kg SOTALOL administered intravenously were studied in 15 subjects aged between 32 and 81 years. The following parameters were recorded: sinus rate (SR), corrected sinus node recovery time (SNRT), sinoatrial conduction time (SACT), PA interval, right atrial effective refractory period (ERP), right atrial functional refractory period (FRP), AH interval at rest, at 100 bpm, Luciani-Wenckebach point (LWP), AV node ERP and FRP, HV interval, His-Purkinje ERP, right ventricular ERP, corrected QT interval. At this dosage, intravenous SOTALOL displays two types of behaviour: --That common to the betablocker drugs: slowing SR by 16%, increasing the AV nodal conduction, increasing the AH interval at rest (5%), at 100 bpm (23%), increasing AV nodal ERP (26%) and FRP (20%), decreasing the LWP (18%). --Other properties: increasing intraatrial PA interval (3%), increasing right atrial ERP (II%), FRP (I7%), increasing right ventricular ERP (8%), increasing His-Purkinje ERP (when measurable) (about 6%), no change in corrected QT interval. At this dosage, SOTALOL exhibits electrophysiological behaviour similar to drugs in Class III (Touboul): those with a "wide electrophysiological spectrum".