Abstract: A tire deflation monitoring system utilizes a device which attaches to the undercarriage of a vehicle adjacent each pneumatically inflated tire which is to be monitored. The device employs a component such as a wheel for rotationally contacting the road surface upon which the vehicle is disposed. When the road surface is contacted, the wheel is forced upwardly, causing contact to be made with an electrical switch that activates an indicator located in the driver's compartment of the vehicle.