An equation of state, applicable to polar substances over vapor and liquid regions, can be obtained by the addition of three polar parameters to the generalized BWR equation of state previously proposed for non-polar or slightly polar substances. The polar parameters are determined for 39 polar substances from vapor pressures and the second virial coefficients, and for 53 polar substances from vapor pressures and their dipole moments. The new equation of state is found to be valid for prediction of various thermodynamic properties, such as vapor pressures, the second virial coefficients, saturated liquid and vapor densities, vaporization entropies, enthalpies, and PVT properties, over wide vapor and liquid regions except near the critical point, i. e., the 1 017 T_r < 1.3 and 1<P_r<3 region.