This work deals with the real-gas isentropic exponents k(p,nu),k(nu,T)k(p,T). These have been calculated for the alternative refrigerants R-123 and R-134a (i.e. the leading proposed replacements for CFC-11 and CFC-12, respectively), as well as for the azeotropic blends R-500 (73.8 wt% R-12 + 26.2 wt% R-152a) and R-503 (40.1 wt% R-23 + 59.9 wt% R-13). Analytical relations, arithmetic values and comparisons are given for a wide range of state conditions. The results should be useful in refrigeration applications.