A Burnett/isochoric PVT apparatus and a metal ebulliometer have been used to measure the gas-phase PVT surface and vapor pressures of 1,1,1-trifluoroethane (R143a). The PVT measurements spanned the temperature range 276 K to 373 K at pressures up to 6.6 MPa (densities to 6 mol . dm(-3)). A virial surface is given which represents the data up to a density of 3.5 mol . dm(-3). Formulations are given for the second and third virial coefficients. Vapor pressure measurements spanned the temperature range 236 K to 343 K. Thermodynamic calculations were used to extend the range down to a temperature of 180 K, and an equation is given which represents the vapor pressure curve from 180 K to the critical temperature. The temperature of the normal boiling point was found to be (225.90 +/- 0.01) K. Comparisons are made with other published results for R143a.