Abstract: A spark plug which has a capacitor located therein, connected in parallel to the main or ignition spark gap (13), additional includes a pilot or pre-spark gap (12) located within the insulator (18) of the spark gap, to control discharge of the capacitor (14) through the main spark gap (13). In accordance with the invention, the pre-spark gap (12) is located within a chamber (34) in the insulator which is filled with a pressurized gas, preferably nitrogen under pressure of between 2 to 100 bar, preferably 5 to 30 bar, with the electrodes (27, 27) defining the pre-spark gap being spaced, preferably, between about 0.1 to 1 mm from each other. Placing the pre-spark gap electrodes within a pressurized gas chamber increases the energy available at the main spark gap (13) for ignition even of very lean fuel-air mixtures.