The invention describes a method for operating glow plugs, that comprise a housing and a heater element projecting beyond that housing, in a diesel engine which interacts with an engine control unit and a glow plug control unit which latter, following a preheating phase, controls the electric power supplied to the glow plugs in response to an input received from the engine control unit. It is provided according to the invention that the engine control unit determines a value representative of a temperature that is to be reached at the heater element and the engine control unit transmits that value as target value to the glow plug control unit which implements that target value using an algorithm stored in the glow plug control unit and with reference to characteristic values stored in the glow plug control unit.