Abstract: An arrangement for detecting the turbocharger rotational speed on internal-combustion engines is provided with at least one piezoelectric acceleration sensor fixed on the turbocharger and with an analyzing circuit having an analog filter arrangement for filtering the output signals of the acceleration sensor. The output signals of the filter arrangement are fed by way of a frequency-to-voltage converter in the form of an analog voltage, or directly in the form of frequency signals, as input signals to an electronic control unit of the internal-combustion engine or to a measuring and/or display unit. As a result, the turbocharger rotational speed can be detected at a reasonable cost with a small and robust arrangement suitable for mass production and requiring no constructional changes on the turbocharger.