Abstract: Refrigerant composition is disclosed which comprises: (a) pentafluoroethane, trifluoromethoxydifluoromethane or hexafluorocyclopropane, or a mixture of two or more thereof, in an amount of at least 75% based on the weight of the composition, (b) 1,1,1,2- or 1,1,2,2-tetrafluoroethane, trifluoromethoxypentafluoroethane, 1,1,1,2,3,3-heptafluoropropane or a mixture of two or more thereof, in an amount of from 10 to 20% by weight based on the weight of the composition and (c) and ethylenically unsaturated or saturated hydrocarbon, optionally containing one or more oxygen atoms, with a boiling point from ?50° C. to +35° C., or a mixture thereof in an amount from 1% to 4% by weight based on the weight of the composition, the weight ratio of component (a): component (b) being at least 4:1.