The invention relates to a method for controlling a safety-critical system, in particular of a motor vehicle, which includes a microcontroller. The microcontroller controls and/or regulates the operating sequences of the safety-critical system, and the microcontroller is composed of a microprocessor and at least one peripheral microprocessor device. In a method for controlling a safety-critical system in which disruption to the operational reliability is to be prevented by changes in the molecular movement of the carrier of the microprocessor, the chip temperature of a chip which is provided with the microprocessor and peripheral device together is measured during an operating sequence and/or program sequence and compared with a maximum permitted chip temperature of the microcontroller. The operating sequence and/or the program sequence is controlled as a function of the temperature comparison.