In a monitoring unit for monitoring position signals of incremental position-measuring devices, at least two position signals are applied on the input side that result from the scanning of an incremental graduation track by a scanning unit and that are out-of-phase with each other. The monitoring unit includes a signal logic unit with which at least two position-dependent status data words are able to be generated from different position signals, and an evaluation unit to which the status data words are supplied, in which invalid statuses are ascertainable by comparing the status data words, and an error signal is able to be generated in response to an ascertained invalid status.