We present modifications to an extended corresponding states (ECS) model for thermal conductivity and viscosity originally developed by Ely and Hanley (Ind. Eng. Chem. Fundam. 1981, 20, 323-332). We apply the method to 17 pure refrigerants and present coefficients for the model and comparisons with experimental data. The average absolute viscosity deviation for the 17 pure fluids studied ranges from a low of 0.56% for R236ea to a high of 5.68% for propylene, with an average absolute deviation for all fluids of 3.13% based on a total of 3737 points. The average absolute thermal conductivity deviation for the 17 pure fluids studied ranges from a low of 1.37% for R116 to a high of 6.78% for R115, with an average absolute deviation for all fluids of 3.75% based on a total of 12 156 points. We also present a new correlation for the viscosity of R134a (1,1,1,2-tetrafluoroethane), which is used as a reference fluid for the description of properties of some refrigerants. The new correlation represents the viscosity to within the uncertainty of the best experimental data.