The paper reports new measurements of the viscosity of liquid difluoromethane (HFC-32) over the temperature range 233.15 K to 333.15 K and the viscosity of pentafluoroethane (HFC-125) over the temperature range 233.15 K to 328.15 K along the saturation line. The viscosities were measured in a calibrated capillary viscometer. A new method was developed to operate the viscometer and to analyze the measured data. The uncertainty of the results is estimated to be no more than 3%. The results were correlated as a function of temperature.