Abstract: An improved ignition circuit for internal combustion engines is described herein, in which a diode is connected in parallel to a primary winding of an ignition coil of a magneto, and a composite transistor circuit consisting of two transistors whose forward direction is directed in the reverse direction of said diode, is connected across said primary winding at its collector and emitter, whereby overheating of said transistors caused by a primary reverse current of said magneto ignition coil flowing into the transistors can be prevented and also proper ignition timing can be maintained.