An ultrasonic monitoring system for the interior of a motor vehicle having two mutually spatially separately secured emission elements (S1, S2), the main lobes of the directional characteristics of which are oriented in different directions, and having at least one reception element (E1, E2), but at as a rule having at least two mutually physically separate reception elements (E1, E2). The reception elements (E1, E2) are not formed by the emission elements (S1, S2), but are physically separate from all emission elements (S1, S2). The two emission elements (S1, S2) are operated alternately with pauses in such a manner that in each instance firstly only one of the emission elements (e.g. S1) emits an ultrasonic pulse, which is thereafter received by the reception element (E1 ) associated with this emission element (S1), and only after such reception does the other emission element (S2) emit ultrasound, which is thereafter received by the reception element (E2) associated with this emission element (S2 ). The main lobes of the directional characteristics of the emission elements (S1, S2) and reception elements (E1, E2) are oriented so that each reception element (E1, E2) receives particularly clearly those emission signals of the emission element (S1, S2) associated with it (E1, E2) which propagate by repeated reflections in each instance via a plurality of panes (VS1/VS2, HS1/HS2) in the V interior of the motor vehicle.