A system for CO.sub.2 cooling of the cargo compartment of a refrigerated vehicle. A vessel carried by the vehicle holds liquid CO.sub.2 at pressure preferably not greater than about 125 psia. Liquid CO.sub.2 is supplied to first heat-exchanger where it is vaporized and warmed a predetermined amount while the pressure is maintained at at least about 80 psia. The pressure of the warmed CO.sub.2 is lowered to about atmospheric pressure without the creation of solid CO.sub.2, while simultaneously cooling the CO.sub.2 vapor, using a gas-driven motor through which the CO.sub.2 vapor is passed. The cooled CO.sub.2 vapor from the motor is passed through a second heat-exchanger, and a fan connected to the motor circulates the atmosphere in the cargo compartment in association with both heat-exchangers. The CO.sub.2 vapor from the second heat-exchanger is vented to the atmosphere exterior of cargo compartment. Isenthalpic expansion means may be used in series with the gas motor, or a second gas motor may be used which can drive a generator to create electric power that is stored in a battery.