Abstract: For a four cylinder engine, there are provided two ignition coil units, each including a primary coil and a secondary coil. The primary coil is wound around a center core made of grain oriented silicon steel, which forms a closed magnetic path for the magnetic flux produced by the coil unit together with a side core formed of non-grain oriented steel as one body. In the closed magnetic path there is provided an air gap. The current of the primary coils is controlled by transistors operated in response to gate signals furnished from an ignition control unit. The transistors are provided with a diode in the reverse parallel therewith. With these arrangements, the ignition coil assembly for an electronic distribution system can be miniaturized with the unfavorable influence of the magnetic inteference suppressed remarkably.