The gaseous PVT properties of ethyl fluoride (HFC-161) were measured at temperatures from 300.16 to 370.15 K and corresponding pressures from 0.6422 to 3.9562 MPa using the isochoric method. The maximum uncertainties were estimated to be within +/- 1.5 kPa for pressure and within +/- 6 mK for temperature. The purity of the HFC-161 sample used in the present measurements was 99.74 wt%. A virial-type equation of state was developed based on the present measurements; this equation reproduced the experimental data in the gas phase within +/- 0.28% in pressure and within +/- 0.38% in density. On the basis of the present PVT properties and vapor pressures measured, saturated vapor densities of HFC-161 were determined, and a correlation of saturated vapor densities was presented. (c) 2005 Elsevier B.V. All rights reserved.