The invention describes a method for controlling glow plugs in diesel engines by varying the effective electric voltage applied to the glow plugs between an initial value and a target value, which is obtained at the end of a cold start phase determined by an engine control unit and which is smaller than the initial value, wherein the increase in voltage, i.e. the voltage difference by which the effective voltage applied to the glow plugs in the cold start phase is higher than its target value, is reduced by steps from a maximum value to zero. The invention provides that the effective electric voltage is increased in the cold start phase of the engine over a predetermined period or time, which is determined by the time elapsed until a preselected number of revolutions of the engine is reached.