Abstract: The invention relates to a refrigeration system that includes a first and a second refrigeration circuit wherein the first refrigeration circuit uses CO2 as the refrigerant, the second refrigeration circuit uses a second refrigerant, and the second refrigeration circuit is arranged to refrigerate the first refrigeration circuit by means of a cascade heat exchange connection. The first refrigerant is at a pressure above about 120 psig. The refrigeration system is energy efficient and is particularly useful in the food industry. The invention further relates to a method of refrigeration using the refrigerator system.