Abstract: An ignition system for an internal combustion engine that has at least two spark plugs for each of the cylinders. The number of spark plugs ignited is controlled in accordance with the operational condition of the engine. The system includes an ignition control means for controlling the ignition in such a manner that an all-point ignition in which all the spark plugs are ignited is carried out in a condition where the temperature of the engine is equal to or lower than a predetermined value, and so that a decreased number-point ignition in which the ignition of at least one of the spark plugs is discontinued is carried out in a condition where the temperature of the engine is higher than the predetermined value.