Abstract: An active seat suspension control system provides for continuous adjustment of the height of a tractor seat in response to movement of a mass within a vibrometer. The vertical position of the vibrometer mass is coupled to adjust one of a pair of potentiometers in a bridge circuit with the other potentiometer being adjusted by the actual height of the seat. During extreme movement of the tractor, the control system is disabled by an arrangement which includes a pair of limit switches at opposite extremes of vertical movement of the vibrometer mass and a circuit which effectively uncouples a source of pressurized fluid to a hydraulic cylinder coupled to adjust the vertical position of the seat. The control system is coupled through the tractor ignition switch to the tractor power supply so as to be disabled except when the ignition switch is turned on.