A method and a device for monitoring a rotational speed of a first charger for an internal combustion engine, especially an exhaust gas turbocharger, are provided. A first exhaust value representing an exhaust gas composition of the internal combustion engine in a first exhaust section is defined, and a first speed value representing the rotational speed of the first charger is determined according to the defined first exhaust value. The first exhaust value is regulated to a predefined first reference value using a first correcting variable which is ascertained as required for regulation. The first rotational speed value is determined depending on the first correcting variable.