Isothermal vapor-liquid equilibrium data of the binary system 1,1-difluoroethane (HFC-152a) + propane (R-290) were measured in the temperature range from 273.15 K to 313.15 K at 10 K intervals and in the composition range from 0.2 to 0.8 mole fraction of propane. The temperature, pressure, and compositions of the liquid and vapor phases were measured with a circulation-type apparatus. The experimental data were correlated with the Carnahan-Starling-De Santis, Peng-Robinson, and Redlich-Kwong-Soave equations of state. Azeotropic behavior was revealed near 0.73 mole fraction of propane. The vapor pressure of the azeotropic system was compared with those of chlorodifluoroethane (HCFC-22) and the zeotropic mixture of difluoroethane (HFC-32) + pentafluoroethane (HFC-125) (50-50) (alternative refrigerant blend R-410A), the zeotropic mixture of HFC-32 + HFC-125 + 1,1,1,2-tetrafluoroethane (HFC-134a) (23-25-52) (alternative refrigerant blend R-407C), dichlorodifluoromethane (HCFC-12), and HFC-134a. It was found that the vapor pressure of the azeotropic system was very close to that of HCFC-22. This azeotropic system has good potential to replace the use of HCFC-22 as a refrigerant.