A closed cycle refrigerating system for cryogenic temperatures using a single stage compressor with a refrigerant comprising a gas mixture. The refrigerating system includes a heat exchanger having a throttling orifice which is arranged to provide refrigeration, and a single stage oil lubricated compressor for compressing the refrigerant. The compressor is typically of the rolling piston type. The refrigerant is a mixture of at least one cryogenic gas having a normal boiling point below 120 degrees K and at least two other gases having normal boiling point temperatures below 300 degrees different from each other and from said one gas. There is also included means for cooling the compressed refrigerant and for circulating the cooled refrigerant to the heat exchanger and its throttling orifice and then back to the compressor. The system does not require any cascaded heat exchangers or intermediate phase separators.