An experimental study of the pressure-volume-temperature-composition (PVTx) properties in the gas phase for binary mixtures of ethyl fluoride (HFC-161)+difluoromethane (HFC-32) was conducted in the range of temperatures from 303.179 to 403.190K, pressures from 1182.9 to 5918.2 kPa, densities from 0.5754 to 3.2174 mol dm(-3), and compositions from 0.1597 to 0.8989 mole fractions of HFC-161. The measurements were performed with an isochoric cell apparatus. The uncertainties in the present work were estimated to be +/- 1.5 kPa for pressure, +/- 6 mK for temperature, and +/- 0.15 % for composition. On the basis of the experimental PVTx property data, a truncated virial equation of state was developed for the binary HFC-161/32 system. This equation reproduced the experimental data in the gas phase within +/-0.457% in pressure. The temperature dependence of the second virial coefficients, including the cross-virial coefficients for this system is also discussed. (c) 2006 Elsevier B.V. All rights reserved.