A method for monitoring a physical variable, in particular the tire pressure, of a wheel fitted on a vehicle is performed when the vehicle travels. The physical variable is measured at the wheel and transmitted to a receiver on the vehicle. An evaluation/storage unit determines and stores a predefined first comparative intensity distribution of the receiving strength of the radio signals at a specified deflection angle between the longitudinal axis of the vehicle and the plane of the wheel and a random sample for the actual intensity distribution of the receiving strength of the radio signals being recorded by the repeated transmission and receiving of a plurality of radio messages.