Abstract: An adjustable seat suspension system for a vehicle seat for a tractor, earth working equipment, or the like, and in which the seat is resiliently supported by a pressurizable air bag. The seat suspension system provides a manually settable lever by means of which the operator can infinitely vary the height adjustment of the seat for a normal operating position, depending on his size. The seat suspension adjusting mechanism includes a valve for regulating the flow of pressurized air to or from the air bag. The arrangement is such that for any vertical height position selected by the operator, the air controlling mechanism permits the seat to oscillate up and down through a given range of movement, say for example six and one-half inches.