Since the introduction of automotive air conditioning, CFC-12 has been the refrigerant of choice due to its unique properties. These include low toxicity, nonflammability, good stability and materials compatibility, oil solubility, as well as good thermodynamic properties. Recent scientific evidence has implicated CFC-12, along with other fully halogenated chlorofluorocarbons (CFCs) in the possible depletion of ozone in the stratosphere. Through the United Nations Environmental Programme, the worldwide supply of all fully halogenated CFCs will be regulated and significantly reduced.HFC-134a, an environmentally acceptable refrigerant is now being developed as the replacement for CFC-12 to be used in air conditioning systems in new automobiles. Due to the difference in the transport and thermodynamic properties of HFC-134a as compared to CFC-12, as well as new lubricants, the performance of HFC-134a will be different. This paper will discuss in-car performance testing of HFC-134a and CFC-12 in a wind tunnel at the same operating conditions. Data presented will include: wind tunnel ambient conditions, vehicle speed, air conditioning system operating conditions, and passenger compartment temperatures.