This experimental study measured the pressure-volume temperature -composition (PVTx) properties in the gas phase for the binary system of dimethyl ether (DME) + 1,1,1,2-tetrafluoroethane (HFC-134a) at temperatures between 313.53 and 383.49 K, pressures between 541.8 and 3170.2 kPa, densities between 0.2311 and 1.4831 mol-dm(-3), and compositions between 0.2326 and 0.8258 mole fractions of HFC-134a by using the isochoric method. The data were obtained with standard uncertainties of 1.5 kPa for pressure, 0.006 K for temperature, and 0.00025 for composition. Further, a truncated virial equation of state was developed for the binary DME/HFC-134a system by data fitting. The deviations generated by this equation turned out to be within +/- 0.13% in pressure and +/- 0.15% in density.