Abstract: A thrust control system for fluid handling rotary machines, such as turbo expanders equipped with a magnetic thrust bearing, includes a magnetic thrust control circuit for providing a thrust signal which is a measure of the magnitude and direction of the thrust force on the thrust bearing. The rotor and stator of the machine have generally axially opposed thrust areas separated by a thrust cavity. Valves are connected between the thrust cavity and high and low pressure fluid sources. A controller, responsive to the thrust signal, controls the valves to selectively conduct fluid between the cavity and the high and low pressure sources to increase or decrease the fluid pressure in the cavity to minimize variations of the thrust force from a preset value which could be zero, for example.