The speed of sound in gaseous difluoromethane (HFC-32, CH2F2) has been measured by means of a spherical acoustic resonator. Sixty-seven speed of sound values were measured with an accuracy of +/-0.01% at temperatures from 273 to 343 K and pressures from 20 to 250 kPa. The ideal-gas specific heats and the second acoustic virial coefficients have been determined on the basis of the speed of sound measurements. The second virial coefficients calculated from the present speed of sound measurements agree satisfactorily with literature values which were determined from pressure-volume-temperature measurements.