An equation of state, in terms of a dimensionless Gibbs energy, has been developed to correlate the thermodynamic properties of benzene in the gas phase. This consists of an equation for the ideal gas properties and a 13-term polynomial in reduced pressure and reciprocal reduced temperature (ITS-90) which was fitted to P(rho)T, enthalpy of evaporation, enthalphy differences, isobaric heat capacity and isothermal Joule-Thomson coefficient data. The equation has been compared with an earlier non-analytic equation of state developed by Goodwin (1988) and with selected experimental data. The range of the equation is from 298 K to 700 K for densities up to 0.0023 mol cm-3, but excluding a region close to the critical point.