Comprehensive and accurate measurements of the saturated-liquid and saturated-vapour densities together with the vapour pressure of pure sulphur hexafluoride were carried out from the temperature T = 224 K (triple-point temperature T-t = 223.555 K) to 0.033 K below the critical temperature (T-c = 318.723 K). Typical values of the total uncertainties of the measurements are: less than or equal to +/-0.01 percent for the vapour pressures, less than or equal to +/-0.015 percent for the saturated liquid densities, and less than or equal to +/-0.016 percent for the saturated-vapour densities. The values for the critical density and the critical pressure (rho(c) = 742.26 kg (.) m(-3), rho(c) = 3.7550 MPa) and the isothermal compressibilities in the critical region close to the phase boundary have also been determined from these measurements. Comparisons with experimental results of previous workers are presented. Using the new values of this work, new correlation equations for the vapour pressure, the saturated-liquid density, and the saturated-vapour density have been established.