Ejector refrigeration systems have attracted many research activities in recent years. These systems traditionally operate with water as refrigerant with low COP values. Other refrigerants commonly used in mechanical vapour compression cycles may provide better performance for ejector refrigeration cycles. Eleven refrigerants, including water, halocarbon compounds (CFCs, HCFCs and HFCs), a cyclic organic compound, and an azeotrope, are chosen as working fluids in an ejector refrigeration system, and their performances are compared. The results show that steam jet systems have very low COP values, the system using R152a as refrigerant has better performance and the variation in COP values for various refrigerants is almost independent of system operating conditions.