We report the results of geometry optimized MP2(FULL)/6-31G(d) quantum chemical calculations with zero-point vibrational energies and thermal corrections of the isomeric 1-, 2-and 9-anthrols and the tautomeric anthrone. We find that 1-and 2-anthrols have nearly the same enthalpy of formation and are some 6 kJ mol À1 more stable than their 9-isomer in accord with intuition based on steric hindrance. We find that anthrone is more stable than 9-anthrol by 13.7 AE 6.4 kJ mol À1 , in satisfactory agreement with the value of 23 AE 8 kJ mol À1 suggested elsewhere by experiment and its associated analysis.