This paper first presents a brief historical summary of the recent past and current status of refrigerants, and then proceeds to suggest a simple Second Law-based approach using the ideal vapor compression refrigeration cycle to estimate a refrigerant's performance potential. The resulting performance rankings are then supplemented by additional rankings of the exergy losses in the compressor and in the condenser. These methodologies are then applied to several refrigerants: three natural refrigerants (ammonia, propane, and isobutane), five conventional single-component halocarbon refrigerants, two conventional blends of halocarbon refrigerants, and three newer refrigerants (fluorinated propene isomers). Generally speaking, the lower pressure refrigerants have better COP and lesser volumetric cooling capacity than the higher pressure refrigerants; whereas, the lower pressure refrigerants have higher penalty factor (measure of condenser exergy losses) than the higher pressure refrigerants. The analyses presented in this paper suggest that to minimize a refrigeration system's overall impact on the environment, the choice of refrigerant should not necessarily be based on a single criterion but rather should be chosen based on the particular application. Copyright © 2013 John Wiley & Sons, Ltd.