The Montreal Protocol and subsequent legislation to control the emission of chlorofluorocarbons (CFC) have mandated the replacement of chlorofluorocarbon refrigerants with hydrofluorocarbon (HFC) refrigerants. This has resulted in the replacement of R-12 refrigerant with R-134a refrigerant. This change is currently being implemented in automotive air conditioning systems. Significant pressures are accelerating me phaseout of the CFC refrigerants.Work with a group of hydrogenated nitrile rubber elastomers, some of which utilize novel polymerization technology and controlled molecular weight distribution, has resulted in some unique materials which are well suited for these types of applications. These hydrogenated polymers were subsequently compounded to yield a new generation of HNBR materials which provide an excellent balance of properties for R-134a refrigerant service.This study will compare these new HNBR's with currently available elastomers in contact with various lubricants and refrigerants. This evaluation will also include permeation resistance, explosive decompression and low-temperature performance. A designed experiment, to optimize permeation resistance, will be evaluated.