A refrigeration system employs mechanical subcooling to substantially increase the efficiency of operation and reduce power consumption. The refrigeration system includes a compressor for compressing a gaseous refrigerant, a condenser for condensing the gaseous refrigerant and subcooling the liquid refrigerant, a receiver for receiving the liquid and a plurality of display cases having evaporators for evaporating the liquid refrigerant.A supplemental subcooling system, including a subcooling evaporator associated with the receiver discharge further subcools the condensed refrigerant before it is passed to the display case evaporators. The compressed gaseous refrigerant is first condensed at a condensing temperature of approximately 10.degree. to 25.degree. F. above a preselected cooling temperature. The condensed liquid is then mechanically subcooled if necessary to the preselected cooling temperature which should be preferably approximately 50.degree. F.